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diff --git a/manual/conf.texi b/manual/conf.texi deleted file mode 100644 index 6700e86539..0000000000 --- a/manual/conf.texi +++ /dev/null @@ -1,1755 +0,0 @@ -@node System Configuration, Cryptographic Functions, System Management, Top -@c %MENU% Parameters describing operating system limits -@chapter System Configuration Parameters - -The functions and macros listed in this chapter give information about -configuration parameters of the operating system---for example, capacity -limits, presence of optional POSIX features, and the default path for -executable files (@pxref{String Parameters}). - -@menu -* General Limits:: Constants and functions that describe - various process-related limits that have - one uniform value for any given machine. -* System Options:: Optional POSIX features. -* Version Supported:: Version numbers of POSIX.1 and POSIX.2. -* Sysconf:: Getting specific configuration values - of general limits and system options. -* Minimums:: Minimum values for general limits. - -* Limits for Files:: Size limitations that pertain to individual files. - These can vary between file systems - or even from file to file. -* Options for Files:: Optional features that some files may support. -* File Minimums:: Minimum values for file limits. -* Pathconf:: Getting the limit values for a particular file. - -* Utility Limits:: Capacity limits of some POSIX.2 utility programs. -* Utility Minimums:: Minimum allowable values of those limits. - -* String Parameters:: Getting the default search path. -@end menu - -@node General Limits -@section General Capacity Limits -@cindex POSIX capacity limits -@cindex limits, POSIX -@cindex capacity limits, POSIX - -The POSIX.1 and POSIX.2 standards specify a number of parameters that -describe capacity limitations of the system. These limits can be fixed -constants for a given operating system, or they can vary from machine to -machine. For example, some limit values may be configurable by the -system administrator, either at run time or by rebuilding the kernel, -and this should not require recompiling application programs. - -@pindex limits.h -Each of the following limit parameters has a macro that is defined in -@file{limits.h} only if the system has a fixed, uniform limit for the -parameter in question. If the system allows different file systems or -files to have different limits, then the macro is undefined; use -@code{sysconf} to find out the limit that applies at a particular time -on a particular machine. @xref{Sysconf}. - -Each of these parameters also has another macro, with a name starting -with @samp{_POSIX}, which gives the lowest value that the limit is -allowed to have on @emph{any} POSIX system. @xref{Minimums}. - -@cindex limits, program argument size -@comment limits.h -@comment POSIX.1 -@deftypevr Macro int ARG_MAX -If defined, the unvarying maximum combined length of the @var{argv} and -@var{environ} arguments that can be passed to the @code{exec} functions. -@end deftypevr - -@cindex limits, number of processes -@comment limits.h -@comment POSIX.1 -@deftypevr Macro int CHILD_MAX -If defined, the unvarying maximum number of processes that can exist -with the same real user ID at any one time. In BSD and GNU, this is -controlled by the @code{RLIMIT_NPROC} resource limit; @pxref{Limits on -Resources}. -@end deftypevr - -@cindex limits, number of open files -@comment limits.h -@comment POSIX.1 -@deftypevr Macro int OPEN_MAX -If defined, the unvarying maximum number of files that a single process -can have open simultaneously. In BSD and GNU, this is controlled -by the @code{RLIMIT_NOFILE} resource limit; @pxref{Limits on Resources}. -@end deftypevr - -@comment limits.h -@comment POSIX.1 -@deftypevr Macro int STREAM_MAX -If defined, the unvarying maximum number of streams that a single -process can have open simultaneously. @xref{Opening Streams}. -@end deftypevr - -@cindex limits, time zone name length -@comment limits.h -@comment POSIX.1 -@deftypevr Macro int TZNAME_MAX -If defined, the unvarying maximum length of a time zone name. -@xref{Time Zone Functions}. -@end deftypevr - -These limit macros are always defined in @file{limits.h}. - -@cindex limits, number of supplementary group IDs -@comment limits.h -@comment POSIX.1 -@deftypevr Macro int NGROUPS_MAX -The maximum number of supplementary group IDs that one process can have. - -The value of this macro is actually a lower bound for the maximum. That -is, you can count on being able to have that many supplementary group -IDs, but a particular machine might let you have even more. You can use -@code{sysconf} to see whether a particular machine will let you have -more (@pxref{Sysconf}). -@end deftypevr - -@comment limits.h -@comment POSIX.1 -@deftypevr Macro ssize_t SSIZE_MAX -The largest value that can fit in an object of type @code{ssize_t}. -Effectively, this is the limit on the number of bytes that can be read -or written in a single operation. - -This macro is defined in all POSIX systems because this limit is never -configurable. -@end deftypevr - -@comment limits.h -@comment POSIX.2 -@deftypevr Macro int RE_DUP_MAX -The largest number of repetitions you are guaranteed is allowed in the -construct @samp{\@{@var{min},@var{max}\@}} in a regular expression. - -The value of this macro is actually a lower bound for the maximum. That -is, you can count on being able to have that many repetitions, but a -particular machine might let you have even more. You can use -@code{sysconf} to see whether a particular machine will let you have -more (@pxref{Sysconf}). And even the value that @code{sysconf} tells -you is just a lower bound---larger values might work. - -This macro is defined in all POSIX.2 systems, because POSIX.2 says it -should always be defined even if there is no specific imposed limit. -@end deftypevr - -@node System Options -@section Overall System Options -@cindex POSIX optional features -@cindex optional POSIX features - -POSIX defines certain system-specific options that not all POSIX systems -support. Since these options are provided in the kernel, not in the -library, simply using @theglibc{} does not guarantee any of these -features are supported; it depends on the system you are using. - -@pindex unistd.h -You can test for the availability of a given option using the macros in -this section, together with the function @code{sysconf}. The macros are -defined only if you include @file{unistd.h}. - -For the following macros, if the macro is defined in @file{unistd.h}, -then the option is supported. Otherwise, the option may or may not be -supported; use @code{sysconf} to find out. @xref{Sysconf}. - -@comment unistd.h -@comment POSIX.1 -@deftypevr Macro int _POSIX_JOB_CONTROL -If this symbol is defined, it indicates that the system supports job -control. Otherwise, the implementation behaves as if all processes -within a session belong to a single process group. @xref{Job Control}. -@end deftypevr - -@comment unistd.h -@comment POSIX.1 -@deftypevr Macro int _POSIX_SAVED_IDS -If this symbol is defined, it indicates that the system remembers the -effective user and group IDs of a process before it executes an -executable file with the set-user-ID or set-group-ID bits set, and that -explicitly changing the effective user or group IDs back to these values -is permitted. If this option is not defined, then if a nonprivileged -process changes its effective user or group ID to the real user or group -ID of the process, it can't change it back again. @xref{Enable/Disable -Setuid}. -@end deftypevr - -For the following macros, if the macro is defined in @file{unistd.h}, -then its value indicates whether the option is supported. A value of -@code{-1} means no, and any other value means yes. If the macro is not -defined, then the option may or may not be supported; use @code{sysconf} -to find out. @xref{Sysconf}. - -@comment unistd.h -@comment POSIX.2 -@deftypevr Macro int _POSIX2_C_DEV -If this symbol is defined, it indicates that the system has the POSIX.2 -C compiler command, @code{c89}. @Theglibc{} always defines this -as @code{1}, on the assumption that you would not have installed it if -you didn't have a C compiler. -@end deftypevr - -@comment unistd.h -@comment POSIX.2 -@deftypevr Macro int _POSIX2_FORT_DEV -If this symbol is defined, it indicates that the system has the POSIX.2 -Fortran compiler command, @code{fort77}. @Theglibc{} never -defines this, because we don't know what the system has. -@end deftypevr - -@comment unistd.h -@comment POSIX.2 -@deftypevr Macro int _POSIX2_FORT_RUN -If this symbol is defined, it indicates that the system has the POSIX.2 -@code{asa} command to interpret Fortran carriage control. @Theglibc{} -never defines this, because we don't know what the system has. -@end deftypevr - -@comment unistd.h -@comment POSIX.2 -@deftypevr Macro int _POSIX2_LOCALEDEF -If this symbol is defined, it indicates that the system has the POSIX.2 -@code{localedef} command. @Theglibc{} never defines this, because -we don't know what the system has. -@end deftypevr - -@comment unistd.h -@comment POSIX.2 -@deftypevr Macro int _POSIX2_SW_DEV -If this symbol is defined, it indicates that the system has the POSIX.2 -commands @code{ar}, @code{make}, and @code{strip}. @Theglibc{} -always defines this as @code{1}, on the assumption that you had to have -@code{ar} and @code{make} to install the library, and it's unlikely that -@code{strip} would be absent when those are present. -@end deftypevr - -@node Version Supported -@section Which Version of POSIX is Supported - -@comment unistd.h -@comment POSIX.1 -@deftypevr Macro {long int} _POSIX_VERSION -This constant represents the version of the POSIX.1 standard to which -the implementation conforms. For an implementation conforming to the -1995 POSIX.1 standard, the value is the integer @code{199506L}. - -@code{_POSIX_VERSION} is always defined (in @file{unistd.h}) in any -POSIX system. - -@strong{Usage Note:} Don't try to test whether the system supports POSIX -by including @file{unistd.h} and then checking whether -@code{_POSIX_VERSION} is defined. On a non-POSIX system, this will -probably fail because there is no @file{unistd.h}. We do not know of -@emph{any} way you can reliably test at compilation time whether your -target system supports POSIX or whether @file{unistd.h} exists. -@end deftypevr - -@comment unistd.h -@comment POSIX.2 -@deftypevr Macro {long int} _POSIX2_C_VERSION -This constant represents the version of the POSIX.2 standard which the -library and system kernel support. We don't know what value this will -be for the first version of the POSIX.2 standard, because the value is -based on the year and month in which the standard is officially adopted. - -The value of this symbol says nothing about the utilities installed on -the system. - -@strong{Usage Note:} You can use this macro to tell whether a POSIX.1 -system library supports POSIX.2 as well. Any POSIX.1 system contains -@file{unistd.h}, so include that file and then test @code{defined -(_POSIX2_C_VERSION)}. -@end deftypevr - -@node Sysconf -@section Using @code{sysconf} - -When your system has configurable system limits, you can use the -@code{sysconf} function to find out the value that applies to any -particular machine. The function and the associated @var{parameter} -constants are declared in the header file @file{unistd.h}. - -@menu -* Sysconf Definition:: Detailed specifications of @code{sysconf}. -* Constants for Sysconf:: The list of parameters @code{sysconf} can read. -* Examples of Sysconf:: How to use @code{sysconf} and the parameter - macros properly together. -@end menu - -@node Sysconf Definition -@subsection Definition of @code{sysconf} - -@comment unistd.h -@comment POSIX.1 -@deftypefun {long int} sysconf (int @var{parameter}) -@safety{@prelim{}@mtsafe{@mtsenv{}}@asunsafe{@asulock{} @ascuheap{}}@acunsafe{@aculock{} @acsmem{} @acsfd{}}} -@c Some parts of the implementation open /proc and /sys files and dirs -@c to collect system details, using fd and stream I/O depending on the -@c case. The returned max value may change over time for NPROCS, -@c NPROCS_CONF, PHYS_PAGES, AVPHYS_PAGES, NGROUPS_MAX, SIGQUEUE_MAX, -@c depending on variable values read from /proc at each call, and from -@c rlimit-obtained values CHILD_MAX, OPEN_MAX, ARG_MAX, SIGQUEUE_MAX. -This function is used to inquire about runtime system parameters. The -@var{parameter} argument should be one of the @samp{_SC_} symbols listed -below. - -The normal return value from @code{sysconf} is the value you requested. -A value of @code{-1} is returned both if the implementation does not -impose a limit, and in case of an error. - -The following @code{errno} error conditions are defined for this function: - -@table @code -@item EINVAL -The value of the @var{parameter} is invalid. -@end table -@end deftypefun - -@node Constants for Sysconf -@subsection Constants for @code{sysconf} Parameters - -Here are the symbolic constants for use as the @var{parameter} argument -to @code{sysconf}. The values are all integer constants (more -specifically, enumeration type values). - -@vtable @code -@comment unistd.h -@comment POSIX.1 -@item _SC_ARG_MAX -Inquire about the parameter corresponding to @code{ARG_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_CHILD_MAX -Inquire about the parameter corresponding to @code{CHILD_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_OPEN_MAX -Inquire about the parameter corresponding to @code{OPEN_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_STREAM_MAX -Inquire about the parameter corresponding to @code{STREAM_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_TZNAME_MAX -Inquire about the parameter corresponding to @code{TZNAME_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_NGROUPS_MAX -Inquire about the parameter corresponding to @code{NGROUPS_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_JOB_CONTROL -Inquire about the parameter corresponding to @code{_POSIX_JOB_CONTROL}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_SAVED_IDS -Inquire about the parameter corresponding to @code{_POSIX_SAVED_IDS}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_VERSION -Inquire about the parameter corresponding to @code{_POSIX_VERSION}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_CLK_TCK -Inquire about the number of clock ticks per second; @pxref{CPU Time}. -The corresponding parameter @code{CLK_TCK} is obsolete. - -@comment unistd.h -@comment GNU -@item _SC_CHARCLASS_NAME_MAX -Inquire about the parameter corresponding to maximal length allowed for -a character class name in an extended locale specification. These -extensions are not yet standardized and so this option is not standardized -as well. - -@comment unistdh.h -@comment POSIX.1 -@item _SC_REALTIME_SIGNALS -Inquire about the parameter corresponding to @code{_POSIX_REALTIME_SIGNALS}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_PRIORITY_SCHEDULING -Inquire about the parameter corresponding to @code{_POSIX_PRIORITY_SCHEDULING}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_TIMERS -Inquire about the parameter corresponding to @code{_POSIX_TIMERS}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_ASYNCHRONOUS_IO -Inquire about the parameter corresponding to @code{_POSIX_ASYNCHRONOUS_IO}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_PRIORITIZED_IO -Inquire about the parameter corresponding to @code{_POSIX_PRIORITIZED_IO}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_SYNCHRONIZED_IO -Inquire about the parameter corresponding to @code{_POSIX_SYNCHRONIZED_IO}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_FSYNC -Inquire about the parameter corresponding to @code{_POSIX_FSYNC}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_MAPPED_FILES -Inquire about the parameter corresponding to @code{_POSIX_MAPPED_FILES}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_MEMLOCK -Inquire about the parameter corresponding to @code{_POSIX_MEMLOCK}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_MEMLOCK_RANGE -Inquire about the parameter corresponding to @code{_POSIX_MEMLOCK_RANGE}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_MEMORY_PROTECTION -Inquire about the parameter corresponding to @code{_POSIX_MEMORY_PROTECTION}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_MESSAGE_PASSING -Inquire about the parameter corresponding to @code{_POSIX_MESSAGE_PASSING}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_SEMAPHORES -Inquire about the parameter corresponding to @code{_POSIX_SEMAPHORES}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_SHARED_MEMORY_OBJECTS -Inquire about the parameter corresponding to@* -@code{_POSIX_SHARED_MEMORY_OBJECTS}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_AIO_LISTIO_MAX -Inquire about the parameter corresponding to @code{_POSIX_AIO_LISTIO_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_AIO_MAX -Inquire about the parameter corresponding to @code{_POSIX_AIO_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_AIO_PRIO_DELTA_MAX -Inquire about the value by which a process can decrease its asynchronous I/O -priority level from its own scheduling priority. This corresponds to the -run-time invariant value @code{AIO_PRIO_DELTA_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_DELAYTIMER_MAX -Inquire about the parameter corresponding to @code{_POSIX_DELAYTIMER_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_MQ_OPEN_MAX -Inquire about the parameter corresponding to @code{_POSIX_MQ_OPEN_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_MQ_PRIO_MAX -Inquire about the parameter corresponding to @code{_POSIX_MQ_PRIO_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_RTSIG_MAX -Inquire about the parameter corresponding to @code{_POSIX_RTSIG_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_SEM_NSEMS_MAX -Inquire about the parameter corresponding to @code{_POSIX_SEM_NSEMS_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_SEM_VALUE_MAX -Inquire about the parameter corresponding to @code{_POSIX_SEM_VALUE_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_SIGQUEUE_MAX -Inquire about the parameter corresponding to @code{_POSIX_SIGQUEUE_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_TIMER_MAX -Inquire about the parameter corresponding to @code{_POSIX_TIMER_MAX}. - -@comment unistd.h -@comment POSIX.1g -@item _SC_PII -Inquire about the parameter corresponding to @code{_POSIX_PII}. - -@comment unistd.h -@comment POSIX.1g -@item _SC_PII_XTI -Inquire about the parameter corresponding to @code{_POSIX_PII_XTI}. - -@comment unistd.h -@comment POSIX.1g -@item _SC_PII_SOCKET -Inquire about the parameter corresponding to @code{_POSIX_PII_SOCKET}. - -@comment unistd.h -@comment POSIX.1g -@item _SC_PII_INTERNET -Inquire about the parameter corresponding to @code{_POSIX_PII_INTERNET}. - -@comment unistd.h -@comment POSIX.1g -@item _SC_PII_OSI -Inquire about the parameter corresponding to @code{_POSIX_PII_OSI}. - -@comment unistd.h -@comment POSIX.1g -@item _SC_SELECT -Inquire about the parameter corresponding to @code{_POSIX_SELECT}. - -@comment unistd.h -@comment POSIX.1g -@item _SC_UIO_MAXIOV -Inquire about the parameter corresponding to @code{_POSIX_UIO_MAXIOV}. - -@comment unistd.h -@comment POSIX.1g -@item _SC_PII_INTERNET_STREAM -Inquire about the parameter corresponding to @code{_POSIX_PII_INTERNET_STREAM}. - -@comment unistd.h -@comment POSIX.1g -@item _SC_PII_INTERNET_DGRAM -Inquire about the parameter corresponding to @code{_POSIX_PII_INTERNET_DGRAM}. - -@comment unistd.h -@comment POSIX.1g -@item _SC_PII_OSI_COTS -Inquire about the parameter corresponding to @code{_POSIX_PII_OSI_COTS}. - -@comment unistd.h -@comment POSIX.1g -@item _SC_PII_OSI_CLTS -Inquire about the parameter corresponding to @code{_POSIX_PII_OSI_CLTS}. - -@comment unistd.h -@comment POSIX.1g -@item _SC_PII_OSI_M -Inquire about the parameter corresponding to @code{_POSIX_PII_OSI_M}. - -@comment unistd.h -@comment POSIX.1g -@item _SC_T_IOV_MAX -Inquire about the value associated with the @code{T_IOV_MAX} -variable. - -@comment unistd.h -@comment POSIX.1 -@item _SC_THREADS -Inquire about the parameter corresponding to @code{_POSIX_THREADS}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_THREAD_SAFE_FUNCTIONS -Inquire about the parameter corresponding to@* -@code{_POSIX_THREAD_SAFE_FUNCTIONS}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_GETGR_R_SIZE_MAX -Inquire about the parameter corresponding to @code{_POSIX_GETGR_R_SIZE_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_GETPW_R_SIZE_MAX -Inquire about the parameter corresponding to @code{_POSIX_GETPW_R_SIZE_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_LOGIN_NAME_MAX -Inquire about the parameter corresponding to @code{_POSIX_LOGIN_NAME_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_TTY_NAME_MAX -Inquire about the parameter corresponding to @code{_POSIX_TTY_NAME_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_THREAD_DESTRUCTOR_ITERATIONS -Inquire about the parameter corresponding to -@code{_POSIX_THREAD_DESTRUCTOR_ITERATIONS}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_THREAD_KEYS_MAX -Inquire about the parameter corresponding to @code{_POSIX_THREAD_KEYS_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_THREAD_STACK_MIN -Inquire about the parameter corresponding to @code{_POSIX_THREAD_STACK_MIN}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_THREAD_THREADS_MAX -Inquire about the parameter corresponding to @code{_POSIX_THREAD_THREADS_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_THREAD_ATTR_STACKADDR -Inquire about the parameter corresponding to@*a -@code{_POSIX_THREAD_ATTR_STACKADDR}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_THREAD_ATTR_STACKSIZE -Inquire about the parameter corresponding to@* -@code{_POSIX_THREAD_ATTR_STACKSIZE}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_THREAD_PRIORITY_SCHEDULING -Inquire about the parameter corresponding to -@code{_POSIX_THREAD_PRIORITY_SCHEDULING}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_THREAD_PRIO_INHERIT -Inquire about the parameter corresponding to @code{_POSIX_THREAD_PRIO_INHERIT}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_THREAD_PRIO_PROTECT -Inquire about the parameter corresponding to @code{_POSIX_THREAD_PRIO_PROTECT}. - -@comment unistd.h -@comment POSIX.1 -@item _SC_THREAD_PROCESS_SHARED -Inquire about the parameter corresponding to -@code{_POSIX_THREAD_PROCESS_SHARED}. - -@comment unistd.h -@comment POSIX.2 -@item _SC_2_C_DEV -Inquire about whether the system has the POSIX.2 C compiler command, -@code{c89}. - -@comment unistd.h -@comment POSIX.2 -@item _SC_2_FORT_DEV -Inquire about whether the system has the POSIX.2 Fortran compiler -command, @code{fort77}. - -@comment unistd.h -@comment POSIX.2 -@item _SC_2_FORT_RUN -Inquire about whether the system has the POSIX.2 @code{asa} command to -interpret Fortran carriage control. - -@comment unistd.h -@comment POSIX.2 -@item _SC_2_LOCALEDEF -Inquire about whether the system has the POSIX.2 @code{localedef} -command. - -@comment unistd.h -@comment POSIX.2 -@item _SC_2_SW_DEV -Inquire about whether the system has the POSIX.2 commands @code{ar}, -@code{make}, and @code{strip}. - -@comment unistd.h -@comment POSIX.2 -@item _SC_BC_BASE_MAX -Inquire about the maximum value of @code{obase} in the @code{bc} -utility. - -@comment unistd.h -@comment POSIX.2 -@item _SC_BC_DIM_MAX -Inquire about the maximum size of an array in the @code{bc} -utility. - -@comment unistd.h -@comment POSIX.2 -@item _SC_BC_SCALE_MAX -Inquire about the maximum value of @code{scale} in the @code{bc} -utility. - -@comment unistd.h -@comment POSIX.2 -@item _SC_BC_STRING_MAX -Inquire about the maximum size of a string constant in the -@code{bc} utility. - -@comment unistd.h -@comment POSIX.2 -@item _SC_COLL_WEIGHTS_MAX -Inquire about the maximum number of weights that can necessarily -be used in defining the collating sequence for a locale. - -@comment unistd.h -@comment POSIX.2 -@item _SC_EXPR_NEST_MAX -Inquire about the maximum number of expressions nested within -parentheses when using the @code{expr} utility. - -@comment unistd.h -@comment POSIX.2 -@item _SC_LINE_MAX -Inquire about the maximum size of a text line that the POSIX.2 text -utilities can handle. - -@comment unistd.h -@comment POSIX.2 -@item _SC_EQUIV_CLASS_MAX -Inquire about the maximum number of weights that can be assigned to an -entry of the @code{LC_COLLATE} category @samp{order} keyword in a locale -definition. @Theglibc{} does not presently support locale -definitions. - -@comment unistd.h -@comment POSIX.2 -@item _SC_VERSION -Inquire about the version number of POSIX.1 that the library and kernel -support. - -@comment unistd.h -@comment POSIX.2 -@item _SC_2_VERSION -Inquire about the version number of POSIX.2 that the system utilities -support. - -@comment unistd.h -@comment GNU -@item _SC_PAGESIZE -Inquire about the virtual memory page size of the machine. -@code{getpagesize} returns the same value (@pxref{Query Memory Parameters}). - -@comment unistd.h -@comment GNU -@item _SC_NPROCESSORS_CONF -Inquire about the number of configured processors. - -@comment unistd.h -@comment GNU -@item _SC_NPROCESSORS_ONLN -Inquire about the number of processors online. - -@comment unistd.h -@comment GNU -@item _SC_PHYS_PAGES -Inquire about the number of physical pages in the system. - -@comment unistd.h -@comment GNU -@item _SC_AVPHYS_PAGES -Inquire about the number of available physical pages in the system. - -@comment unistd.h -@comment GNU -@item _SC_ATEXIT_MAX -Inquire about the number of functions which can be registered as termination -functions for @code{atexit}; @pxref{Cleanups on Exit}. - -@comment unistd.h -@comment X/Open -@item _SC_XOPEN_VERSION -Inquire about the parameter corresponding to @code{_XOPEN_VERSION}. - -@comment unistd.h -@comment X/Open -@item _SC_XOPEN_XCU_VERSION -Inquire about the parameter corresponding to @code{_XOPEN_XCU_VERSION}. - -@comment unistd.h -@comment X/Open -@item _SC_XOPEN_UNIX -Inquire about the parameter corresponding to @code{_XOPEN_UNIX}. - -@comment unistd.h -@comment X/Open -@item _SC_XOPEN_REALTIME -Inquire about the parameter corresponding to @code{_XOPEN_REALTIME}. - -@comment unistd.h -@comment X/Open -@item _SC_XOPEN_REALTIME_THREADS -Inquire about the parameter corresponding to @code{_XOPEN_REALTIME_THREADS}. - -@comment unistd.h -@comment X/Open -@item _SC_XOPEN_LEGACY -Inquire about the parameter corresponding to @code{_XOPEN_LEGACY}. - -@comment unistd.h -@comment X/Open -@item _SC_XOPEN_CRYPT -Inquire about the parameter corresponding to @code{_XOPEN_CRYPT}. - -@comment unistd.h -@comment X/Open -@item _SC_XOPEN_ENH_I18N -Inquire about the parameter corresponding to @code{_XOPEN_ENH_I18N}. - -@comment unistd.h -@comment X/Open -@item _SC_XOPEN_SHM -Inquire about the parameter corresponding to @code{_XOPEN_SHM}. - -@comment unistd.h -@comment X/Open -@item _SC_XOPEN_XPG2 -Inquire about the parameter corresponding to @code{_XOPEN_XPG2}. - -@comment unistd.h -@comment X/Open -@item _SC_XOPEN_XPG3 -Inquire about the parameter corresponding to @code{_XOPEN_XPG3}. - -@comment unistd.h -@comment X/Open -@item _SC_XOPEN_XPG4 -Inquire about the parameter corresponding to @code{_XOPEN_XPG4}. - -@comment unistd.h -@comment X/Open -@item _SC_CHAR_BIT -Inquire about the number of bits in a variable of type @code{char}. - -@comment unistd.h -@comment X/Open -@item _SC_CHAR_MAX -Inquire about the maximum value which can be stored in a variable of type -@code{char}. - -@comment unistd.h -@comment X/Open -@item _SC_CHAR_MIN -Inquire about the minimum value which can be stored in a variable of type -@code{char}. - -@comment unistd.h -@comment X/Open -@item _SC_INT_MAX -Inquire about the maximum value which can be stored in a variable of type -@code{int}. - -@comment unistd.h -@comment X/Open -@item _SC_INT_MIN -Inquire about the minimum value which can be stored in a variable of type -@code{int}. - -@comment unistd.h -@comment X/Open -@item _SC_LONG_BIT -Inquire about the number of bits in a variable of type @code{long int}. - -@comment unistd.h -@comment X/Open -@item _SC_WORD_BIT -Inquire about the number of bits in a variable of a register word. - -@comment unistd.h -@comment X/Open -@item _SC_MB_LEN_MAX -Inquire about the maximum length of a multi-byte representation of a wide -character value. - -@comment unistd.h -@comment X/Open -@item _SC_NZERO -Inquire about the value used to internally represent the zero priority level for -the process execution. - -@comment unistd.h -@comment X/Open -@item SC_SSIZE_MAX -Inquire about the maximum value which can be stored in a variable of type -@code{ssize_t}. - -@comment unistd.h -@comment X/Open -@item _SC_SCHAR_MAX -Inquire about the maximum value which can be stored in a variable of type -@code{signed char}. - -@comment unistd.h -@comment X/Open -@item _SC_SCHAR_MIN -Inquire about the minimum value which can be stored in a variable of type -@code{signed char}. - -@comment unistd.h -@comment X/Open -@item _SC_SHRT_MAX -Inquire about the maximum value which can be stored in a variable of type -@code{short int}. - -@comment unistd.h -@comment X/Open -@item _SC_SHRT_MIN -Inquire about the minimum value which can be stored in a variable of type -@code{short int}. - -@comment unistd.h -@comment X/Open -@item _SC_UCHAR_MAX -Inquire about the maximum value which can be stored in a variable of type -@code{unsigned char}. - -@comment unistd.h -@comment X/Open -@item _SC_UINT_MAX -Inquire about the maximum value which can be stored in a variable of type -@code{unsigned int}. - -@comment unistd.h -@comment X/Open -@item _SC_ULONG_MAX -Inquire about the maximum value which can be stored in a variable of type -@code{unsigned long int}. - -@comment unistd.h -@comment X/Open -@item _SC_USHRT_MAX -Inquire about the maximum value which can be stored in a variable of type -@code{unsigned short int}. - -@comment unistd.h -@comment X/Open -@item _SC_NL_ARGMAX -Inquire about the parameter corresponding to @code{NL_ARGMAX}. - -@comment unistd.h -@comment X/Open -@item _SC_NL_LANGMAX -Inquire about the parameter corresponding to @code{NL_LANGMAX}. - -@comment unistd.h -@comment X/Open -@item _SC_NL_MSGMAX -Inquire about the parameter corresponding to @code{NL_MSGMAX}. - -@comment unistd.h -@comment X/Open -@item _SC_NL_NMAX -Inquire about the parameter corresponding to @code{NL_NMAX}. - -@comment unistd.h -@comment X/Open -@item _SC_NL_SETMAX -Inquire about the parameter corresponding to @code{NL_SETMAX}. - -@comment unistd.h -@comment X/Open -@item _SC_NL_TEXTMAX -Inquire about the parameter corresponding to @code{NL_TEXTMAX}. -@end vtable - -@node Examples of Sysconf -@subsection Examples of @code{sysconf} - -We recommend that you first test for a macro definition for the -parameter you are interested in, and call @code{sysconf} only if the -macro is not defined. For example, here is how to test whether job -control is supported: - -@smallexample -@group -int -have_job_control (void) -@{ -#ifdef _POSIX_JOB_CONTROL - return 1; -#else - int value = sysconf (_SC_JOB_CONTROL); - if (value < 0) - /* @r{If the system is that badly wedged,} - @r{there's no use trying to go on.} */ - fatal (strerror (errno)); - return value; -#endif -@} -@end group -@end smallexample - -Here is how to get the value of a numeric limit: - -@smallexample -int -get_child_max () -@{ -#ifdef CHILD_MAX - return CHILD_MAX; -#else - int value = sysconf (_SC_CHILD_MAX); - if (value < 0) - fatal (strerror (errno)); - return value; -#endif -@} -@end smallexample - -@node Minimums -@section Minimum Values for General Capacity Limits - -Here are the names for the POSIX minimum upper bounds for the system -limit parameters. The significance of these values is that you can -safely push to these limits without checking whether the particular -system you are using can go that far. - -@vtable @code -@comment limits.h -@comment POSIX.1 -@item _POSIX_AIO_LISTIO_MAX -The most restrictive limit permitted by POSIX for the maximum number of -I/O operations that can be specified in a list I/O call. The value of -this constant is @code{2}; thus you can add up to two new entries -of the list of outstanding operations. - -@comment limits.h -@comment POSIX.1 -@item _POSIX_AIO_MAX -The most restrictive limit permitted by POSIX for the maximum number of -outstanding asynchronous I/O operations. The value of this constant is -@code{1}. So you cannot expect that you can issue more than one -operation and immediately continue with the normal work, receiving the -notifications asynchronously. - -@comment limits.h -@comment POSIX.1 -@item _POSIX_ARG_MAX -The value of this macro is the most restrictive limit permitted by POSIX -for the maximum combined length of the @var{argv} and @var{environ} -arguments that can be passed to the @code{exec} functions. -Its value is @code{4096}. - -@comment limits.h -@comment POSIX.1 -@item _POSIX_CHILD_MAX -The value of this macro is the most restrictive limit permitted by POSIX -for the maximum number of simultaneous processes per real user ID. Its -value is @code{6}. - -@comment limits.h -@comment POSIX.1 -@item _POSIX_NGROUPS_MAX -The value of this macro is the most restrictive limit permitted by POSIX -for the maximum number of supplementary group IDs per process. Its -value is @code{0}. - -@comment limits.h -@comment POSIX.1 -@item _POSIX_OPEN_MAX -The value of this macro is the most restrictive limit permitted by POSIX -for the maximum number of files that a single process can have open -simultaneously. Its value is @code{16}. - -@comment limits.h -@comment POSIX.1 -@item _POSIX_SSIZE_MAX -The value of this macro is the most restrictive limit permitted by POSIX -for the maximum value that can be stored in an object of type -@code{ssize_t}. Its value is @code{32767}. - -@comment limits.h -@comment POSIX.1 -@item _POSIX_STREAM_MAX -The value of this macro is the most restrictive limit permitted by POSIX -for the maximum number of streams that a single process can have open -simultaneously. Its value is @code{8}. - -@comment limits.h -@comment POSIX.1 -@item _POSIX_TZNAME_MAX -The value of this macro is the most restrictive limit permitted by POSIX -for the maximum length of a time zone name. Its value is @code{3}. - -@comment limits.h -@comment POSIX.2 -@item _POSIX2_RE_DUP_MAX -The value of this macro is the most restrictive limit permitted by POSIX -for the numbers used in the @samp{\@{@var{min},@var{max}\@}} construct -in a regular expression. Its value is @code{255}. -@end vtable - -@node Limits for Files -@section Limits on File System Capacity - -The POSIX.1 standard specifies a number of parameters that describe the -limitations of the file system. It's possible for the system to have a -fixed, uniform limit for a parameter, but this isn't the usual case. On -most systems, it's possible for different file systems (and, for some -parameters, even different files) to have different maximum limits. For -example, this is very likely if you use NFS to mount some of the file -systems from other machines. - -@pindex limits.h -Each of the following macros is defined in @file{limits.h} only if the -system has a fixed, uniform limit for the parameter in question. If the -system allows different file systems or files to have different limits, -then the macro is undefined; use @code{pathconf} or @code{fpathconf} to -find out the limit that applies to a particular file. @xref{Pathconf}. - -Each parameter also has another macro, with a name starting with -@samp{_POSIX}, which gives the lowest value that the limit is allowed to -have on @emph{any} POSIX system. @xref{File Minimums}. - -@cindex limits, link count of files -@comment limits.h (optional) -@comment POSIX.1 -@deftypevr Macro int LINK_MAX -The uniform system limit (if any) for the number of names for a given -file. @xref{Hard Links}. -@end deftypevr - -@cindex limits, terminal input queue -@comment limits.h -@comment POSIX.1 -@deftypevr Macro int MAX_CANON -The uniform system limit (if any) for the amount of text in a line of -input when input editing is enabled. @xref{Canonical or Not}. -@end deftypevr - -@comment limits.h -@comment POSIX.1 -@deftypevr Macro int MAX_INPUT -The uniform system limit (if any) for the total number of characters -typed ahead as input. @xref{I/O Queues}. -@end deftypevr - -@cindex limits, file name length -@comment limits.h -@comment POSIX.1 -@deftypevr Macro int NAME_MAX -The uniform system limit (if any) for the length of a file name component, not -including the terminating null character. - -@strong{Portability Note:} On some systems, @theglibc{} defines -@code{NAME_MAX}, but does not actually enforce this limit. -@end deftypevr - -@comment limits.h -@comment POSIX.1 -@deftypevr Macro int PATH_MAX -The uniform system limit (if any) for the length of an entire file name (that -is, the argument given to system calls such as @code{open}), including the -terminating null character. - -@strong{Portability Note:} @Theglibc{} does not enforce this limit -even if @code{PATH_MAX} is defined. -@end deftypevr - -@cindex limits, pipe buffer size -@comment limits.h -@comment POSIX.1 -@deftypevr Macro int PIPE_BUF -The uniform system limit (if any) for the number of bytes that can be -written atomically to a pipe. If multiple processes are writing to the -same pipe simultaneously, output from different processes might be -interleaved in chunks of this size. @xref{Pipes and FIFOs}. -@end deftypevr - -These are alternative macro names for some of the same information. - -@comment dirent.h -@comment BSD -@deftypevr Macro int MAXNAMLEN -This is the BSD name for @code{NAME_MAX}. It is defined in -@file{dirent.h}. -@end deftypevr - -@comment stdio.h -@comment ISO -@deftypevr Macro int FILENAME_MAX -The value of this macro is an integer constant expression that -represents the maximum length of a file name string. It is defined in -@file{stdio.h}. - -Unlike @code{PATH_MAX}, this macro is defined even if there is no actual -limit imposed. In such a case, its value is typically a very large -number. @strong{This is always the case on @gnuhurdsystems{}.} - -@strong{Usage Note:} Don't use @code{FILENAME_MAX} as the size of an -array in which to store a file name! You can't possibly make an array -that big! Use dynamic allocation (@pxref{Memory Allocation}) instead. -@end deftypevr - -@node Options for Files -@section Optional Features in File Support - -POSIX defines certain system-specific options in the system calls for -operating on files. Some systems support these options and others do -not. Since these options are provided in the kernel, not in the -library, simply using @theglibc{} does not guarantee that any of these -features is supported; it depends on the system you are using. They can -also vary between file systems on a single machine. - -@pindex unistd.h -This section describes the macros you can test to determine whether a -particular option is supported on your machine. If a given macro is -defined in @file{unistd.h}, then its value says whether the -corresponding feature is supported. (A value of @code{-1} indicates no; -any other value indicates yes.) If the macro is undefined, it means -particular files may or may not support the feature. - -Since all the machines that support @theglibc{} also support NFS, -one can never make a general statement about whether all file systems -support the @code{_POSIX_CHOWN_RESTRICTED} and @code{_POSIX_NO_TRUNC} -features. So these names are never defined as macros in @theglibc{}. - -@comment unistd.h -@comment POSIX.1 -@deftypevr Macro int _POSIX_CHOWN_RESTRICTED -If this option is in effect, the @code{chown} function is restricted so -that the only changes permitted to nonprivileged processes is to change -the group owner of a file to either be the effective group ID of the -process, or one of its supplementary group IDs. @xref{File Owner}. -@end deftypevr - -@comment unistd.h -@comment POSIX.1 -@deftypevr Macro int _POSIX_NO_TRUNC -If this option is in effect, file name components longer than -@code{NAME_MAX} generate an @code{ENAMETOOLONG} error. Otherwise, file -name components that are too long are silently truncated. -@end deftypevr - -@comment unistd.h -@comment POSIX.1 -@deftypevr Macro {unsigned char} _POSIX_VDISABLE -This option is only meaningful for files that are terminal devices. -If it is enabled, then handling for special control characters can -be disabled individually. @xref{Special Characters}. -@end deftypevr - -@pindex unistd.h -If one of these macros is undefined, that means that the option might be -in effect for some files and not for others. To inquire about a -particular file, call @code{pathconf} or @code{fpathconf}. -@xref{Pathconf}. - -@node File Minimums -@section Minimum Values for File System Limits - -Here are the names for the POSIX minimum upper bounds for some of the -above parameters. The significance of these values is that you can -safely push to these limits without checking whether the particular -system you are using can go that far. In most cases @gnusystems{} do not -have these strict limitations. The actual limit should be requested if -necessary. - -@vtable @code -@comment limits.h -@comment POSIX.1 -@item _POSIX_LINK_MAX -The most restrictive limit permitted by POSIX for the maximum value of a -file's link count. The value of this constant is @code{8}; thus, you -can always make up to eight names for a file without running into a -system limit. - -@comment limits.h -@comment POSIX.1 -@item _POSIX_MAX_CANON -The most restrictive limit permitted by POSIX for the maximum number of -bytes in a canonical input line from a terminal device. The value of -this constant is @code{255}. - -@comment limits.h -@comment POSIX.1 -@item _POSIX_MAX_INPUT -The most restrictive limit permitted by POSIX for the maximum number of -bytes in a terminal device input queue (or typeahead buffer). -@xref{Input Modes}. The value of this constant is @code{255}. - -@comment limits.h -@comment POSIX.1 -@item _POSIX_NAME_MAX -The most restrictive limit permitted by POSIX for the maximum number of -bytes in a file name component. The value of this constant is -@code{14}. - -@comment limits.h -@comment POSIX.1 -@item _POSIX_PATH_MAX -The most restrictive limit permitted by POSIX for the maximum number of -bytes in a file name. The value of this constant is @code{256}. - -@comment limits.h -@comment POSIX.1 -@item _POSIX_PIPE_BUF -The most restrictive limit permitted by POSIX for the maximum number of -bytes that can be written atomically to a pipe. The value of this -constant is @code{512}. - -@comment limits.h -@comment POSIX.1 -@item SYMLINK_MAX -Maximum number of bytes in a symbolic link. - -@comment limits.h -@comment POSIX.1 -@item POSIX_REC_INCR_XFER_SIZE -Recommended increment for file transfer sizes between the -@code{POSIX_REC_MIN_XFER_SIZE} and @code{POSIX_REC_MAX_XFER_SIZE} -values. - -@comment limits.h -@comment POSIX.1 -@item POSIX_REC_MAX_XFER_SIZE -Maximum recommended file transfer size. - -@comment limits.h -@comment POSIX.1 -@item POSIX_REC_MIN_XFER_SIZE -Minimum recommended file transfer size. - -@comment limits.h -@comment POSIX.1 -@item POSIX_REC_XFER_ALIGN -Recommended file transfer buffer alignment. -@end vtable - -@node Pathconf -@section Using @code{pathconf} - -When your machine allows different files to have different values for a -file system parameter, you can use the functions in this section to find -out the value that applies to any particular file. - -These functions and the associated constants for the @var{parameter} -argument are declared in the header file @file{unistd.h}. - -@comment unistd.h -@comment POSIX.1 -@deftypefun {long int} pathconf (const char *@var{filename}, int @var{parameter}) -@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{} @ascuheap{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}} -@c When __statfs_link_max finds an ext* filesystem, it may read -@c /proc/mounts or similar as a mntent stream. -@c __statfs_chown_restricted may read from -@c /proc/sys/fs/xfs/restrict_chown as a file descriptor. -This function is used to inquire about the limits that apply to -the file named @var{filename}. - -The @var{parameter} argument should be one of the @samp{_PC_} constants -listed below. - -The normal return value from @code{pathconf} is the value you requested. -A value of @code{-1} is returned both if the implementation does not -impose a limit, and in case of an error. In the former case, -@code{errno} is not set, while in the latter case, @code{errno} is set -to indicate the cause of the problem. So the only way to use this -function robustly is to store @code{0} into @code{errno} just before -calling it. - -Besides the usual file name errors (@pxref{File Name Errors}), -the following error condition is defined for this function: - -@table @code -@item EINVAL -The value of @var{parameter} is invalid, or the implementation doesn't -support the @var{parameter} for the specific file. -@end table -@end deftypefun - -@comment unistd.h -@comment POSIX.1 -@deftypefun {long int} fpathconf (int @var{filedes}, int @var{parameter}) -@safety{@prelim{}@mtsafe{}@asunsafe{@asulock{} @ascuheap{}}@acunsafe{@aculock{} @acsfd{} @acsmem{}}} -@c Same caveats as pathconf. -This is just like @code{pathconf} except that an open file descriptor -is used to specify the file for which information is requested, instead -of a file name. - -The following @code{errno} error conditions are defined for this function: - -@table @code -@item EBADF -The @var{filedes} argument is not a valid file descriptor. - -@item EINVAL -The value of @var{parameter} is invalid, or the implementation doesn't -support the @var{parameter} for the specific file. -@end table -@end deftypefun - -Here are the symbolic constants that you can use as the @var{parameter} -argument to @code{pathconf} and @code{fpathconf}. The values are all -integer constants. - -@vtable @code -@comment unistd.h -@comment POSIX.1 -@item _PC_LINK_MAX -Inquire about the value of @code{LINK_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _PC_MAX_CANON -Inquire about the value of @code{MAX_CANON}. - -@comment unistd.h -@comment POSIX.1 -@item _PC_MAX_INPUT -Inquire about the value of @code{MAX_INPUT}. - -@comment unistd.h -@comment POSIX.1 -@item _PC_NAME_MAX -Inquire about the value of @code{NAME_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _PC_PATH_MAX -Inquire about the value of @code{PATH_MAX}. - -@comment unistd.h -@comment POSIX.1 -@item _PC_PIPE_BUF -Inquire about the value of @code{PIPE_BUF}. - -@comment unistd.h -@comment POSIX.1 -@item _PC_CHOWN_RESTRICTED -Inquire about the value of @code{_POSIX_CHOWN_RESTRICTED}. - -@comment unistd.h -@comment POSIX.1 -@item _PC_NO_TRUNC -Inquire about the value of @code{_POSIX_NO_TRUNC}. - -@comment unistd.h -@comment POSIX.1 -@item _PC_VDISABLE -Inquire about the value of @code{_POSIX_VDISABLE}. - -@comment unistd.h -@comment POSIX.1 -@item _PC_SYNC_IO -Inquire about the value of @code{_POSIX_SYNC_IO}. - -@comment unistd.h -@comment POSIX.1 -@item _PC_ASYNC_IO -Inquire about the value of @code{_POSIX_ASYNC_IO}. - -@comment unistd.h -@comment POSIX.1 -@item _PC_PRIO_IO -Inquire about the value of @code{_POSIX_PRIO_IO}. - -@comment unistd.h -@comment LFS -@item _PC_FILESIZEBITS -Inquire about the availability of large files on the filesystem. - -@comment unistd.h -@comment POSIX.1 -@item _PC_REC_INCR_XFER_SIZE -Inquire about the value of @code{POSIX_REC_INCR_XFER_SIZE}. - -@comment unistd.h -@comment POSIX.1 -@item _PC_REC_MAX_XFER_SIZE -Inquire about the value of @code{POSIX_REC_MAX_XFER_SIZE}. - -@comment unistd.h -@comment POSIX.1 -@item _PC_REC_MIN_XFER_SIZE -Inquire about the value of @code{POSIX_REC_MIN_XFER_SIZE}. - -@comment unistd.h -@comment POSIX.1 -@item _PC_REC_XFER_ALIGN -Inquire about the value of @code{POSIX_REC_XFER_ALIGN}. -@end vtable - -@strong{Portability Note:} On some systems, @theglibc{} does not -enforce @code{_PC_NAME_MAX} or @code{_PC_PATH_MAX} limits. - -@node Utility Limits -@section Utility Program Capacity Limits - -The POSIX.2 standard specifies certain system limits that you can access -through @code{sysconf} that apply to utility behavior rather than the -behavior of the library or the operating system. - -@Theglibc{} defines macros for these limits, and @code{sysconf} -returns values for them if you ask; but these values convey no -meaningful information. They are simply the smallest values that -POSIX.2 permits. - -@comment limits.h -@comment POSIX.2 -@deftypevr Macro int BC_BASE_MAX -The largest value of @code{obase} that the @code{bc} utility is -guaranteed to support. -@end deftypevr - -@comment limits.h -@comment POSIX.2 -@deftypevr Macro int BC_DIM_MAX -The largest number of elements in one array that the @code{bc} utility -is guaranteed to support. -@end deftypevr - -@comment limits.h -@comment POSIX.2 -@deftypevr Macro int BC_SCALE_MAX -The largest value of @code{scale} that the @code{bc} utility is -guaranteed to support. -@end deftypevr - -@comment limits.h -@comment POSIX.2 -@deftypevr Macro int BC_STRING_MAX -The largest number of characters in one string constant that the -@code{bc} utility is guaranteed to support. -@end deftypevr - -@comment limits.h -@comment POSIX.2 -@deftypevr Macro int COLL_WEIGHTS_MAX -The largest number of weights that can necessarily be used in defining -the collating sequence for a locale. -@end deftypevr - -@comment limits.h -@comment POSIX.2 -@deftypevr Macro int EXPR_NEST_MAX -The maximum number of expressions that can be nested within parentheses -by the @code{expr} utility. -@end deftypevr - -@comment limits.h -@comment POSIX.2 -@deftypevr Macro int LINE_MAX -The largest text line that the text-oriented POSIX.2 utilities can -support. (If you are using the GNU versions of these utilities, then -there is no actual limit except that imposed by the available virtual -memory, but there is no way that the library can tell you this.) -@end deftypevr - -@comment limits.h -@comment POSIX.2 -@deftypevr Macro int EQUIV_CLASS_MAX -The maximum number of weights that can be assigned to an entry of the -@code{LC_COLLATE} category @samp{order} keyword in a locale definition. -@Theglibc{} does not presently support locale definitions. -@end deftypevr - -@node Utility Minimums -@section Minimum Values for Utility Limits - -@vtable @code -@comment limits.h -@comment POSIX.2 -@item _POSIX2_BC_BASE_MAX -The most restrictive limit permitted by POSIX.2 for the maximum value of -@code{obase} in the @code{bc} utility. Its value is @code{99}. - -@comment limits.h -@comment POSIX.2 -@item _POSIX2_BC_DIM_MAX -The most restrictive limit permitted by POSIX.2 for the maximum size of -an array in the @code{bc} utility. Its value is @code{2048}. - -@comment limits.h -@comment POSIX.2 -@item _POSIX2_BC_SCALE_MAX -The most restrictive limit permitted by POSIX.2 for the maximum value of -@code{scale} in the @code{bc} utility. Its value is @code{99}. - -@comment limits.h -@comment POSIX.2 -@item _POSIX2_BC_STRING_MAX -The most restrictive limit permitted by POSIX.2 for the maximum size of -a string constant in the @code{bc} utility. Its value is @code{1000}. - -@comment limits.h -@comment POSIX.2 -@item _POSIX2_COLL_WEIGHTS_MAX -The most restrictive limit permitted by POSIX.2 for the maximum number -of weights that can necessarily be used in defining the collating -sequence for a locale. Its value is @code{2}. - -@comment limits.h -@comment POSIX.2 -@item _POSIX2_EXPR_NEST_MAX -The most restrictive limit permitted by POSIX.2 for the maximum number -of expressions nested within parenthesis when using the @code{expr} utility. -Its value is @code{32}. - -@comment limits.h -@comment POSIX.2 -@item _POSIX2_LINE_MAX -The most restrictive limit permitted by POSIX.2 for the maximum size of -a text line that the text utilities can handle. Its value is -@code{2048}. - -@comment limits.h -@comment POSIX.2 -@item _POSIX2_EQUIV_CLASS_MAX -The most restrictive limit permitted by POSIX.2 for the maximum number -of weights that can be assigned to an entry of the @code{LC_COLLATE} -category @samp{order} keyword in a locale definition. Its value is -@code{2}. @Theglibc{} does not presently support locale -definitions. -@end vtable - -@node String Parameters -@section String-Valued Parameters - -POSIX.2 defines a way to get string-valued parameters from the operating -system with the function @code{confstr}: - -@comment unistd.h -@comment POSIX.2 -@deftypefun size_t confstr (int @var{parameter}, char *@var{buf}, size_t @var{len}) -@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}} -This function reads the value of a string-valued system parameter, -storing the string into @var{len} bytes of memory space starting at -@var{buf}. The @var{parameter} argument should be one of the -@samp{_CS_} symbols listed below. - -The normal return value from @code{confstr} is the length of the string -value that you asked for. If you supply a null pointer for @var{buf}, -then @code{confstr} does not try to store the string; it just returns -its length. A value of @code{0} indicates an error. - -If the string you asked for is too long for the buffer (that is, longer -than @code{@var{len} - 1}), then @code{confstr} stores just that much -(leaving room for the terminating null character). You can tell that -this has happened because @code{confstr} returns a value greater than or -equal to @var{len}. - -The following @code{errno} error conditions are defined for this function: - -@table @code -@item EINVAL -The value of the @var{parameter} is invalid. -@end table -@end deftypefun - -Currently there is just one parameter you can read with @code{confstr}: - -@vtable @code -@comment unistd.h -@comment POSIX.2 -@item _CS_PATH -This parameter's value is the recommended default path for searching for -executable files. This is the path that a user has by default just -after logging in. - -@comment unistd.h -@comment Unix98 -@item _CS_LFS_CFLAGS -The returned string specifies which additional flags must be given to -the C compiler if a source is compiled using the -@code{_LARGEFILE_SOURCE} feature select macro; @pxref{Feature Test Macros}. - -@comment unistd.h -@comment Unix98 -@item _CS_LFS_LDFLAGS -The returned string specifies which additional flags must be given to -the linker if a source is compiled using the -@code{_LARGEFILE_SOURCE} feature select macro; @pxref{Feature Test Macros}. - -@comment unistd.h -@comment Unix98 -@item _CS_LFS_LIBS -The returned string specifies which additional libraries must be linked -to the application if a source is compiled using the -@code{_LARGEFILE_SOURCE} feature select macro; @pxref{Feature Test Macros}. - -@comment unistd.h -@comment Unix98 -@item _CS_LFS_LINTFLAGS -The returned string specifies which additional flags must be given to -the lint tool if a source is compiled using the -@code{_LARGEFILE_SOURCE} feature select macro; @pxref{Feature Test Macros}. - -@comment unistd.h -@comment Unix98 -@item _CS_LFS64_CFLAGS -The returned string specifies which additional flags must be given to -the C compiler if a source is compiled using the -@code{_LARGEFILE64_SOURCE} feature select macro; @pxref{Feature Test Macros}. - -@comment unistd.h -@comment Unix98 -@item _CS_LFS64_LDFLAGS -The returned string specifies which additional flags must be given to -the linker if a source is compiled using the -@code{_LARGEFILE64_SOURCE} feature select macro; @pxref{Feature Test Macros}. - -@comment unistd.h -@comment Unix98 -@item _CS_LFS64_LIBS -The returned string specifies which additional libraries must be linked -to the application if a source is compiled using the -@code{_LARGEFILE64_SOURCE} feature select macro; @pxref{Feature Test Macros}. - -@comment unistd.h -@comment Unix98 -@item _CS_LFS64_LINTFLAGS -The returned string specifies which additional flags must be given to -the lint tool if a source is compiled using the -@code{_LARGEFILE64_SOURCE} feature select macro; @pxref{Feature Test Macros}. -@end vtable - -The way to use @code{confstr} without any arbitrary limit on string size -is to call it twice: first call it to get the length, allocate the -buffer accordingly, and then call @code{confstr} again to fill the -buffer, like this: - -@smallexample -@group -char * -get_default_path (void) -@{ - size_t len = confstr (_CS_PATH, NULL, 0); - char *buffer = (char *) xmalloc (len); - - if (confstr (_CS_PATH, buf, len + 1) == 0) - @{ - free (buffer); - return NULL; - @} - - return buffer; -@} -@end group -@end smallexample |