GNU/Linux man pages

Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :

ISBN : 978-2-7460-9712-4
EAN : 9782746097124
(Editions ENI)


CentOS 2.1AS







sysconf − Get configuration information at runtime


#include <unistd.h>

long sysconf(int name);


sysconf() provides a way for the application to determine values for system limits or options at runtime.

The equivalent macros defined in <unistd.h> can only give conservative values; if an application wants to take advantage of values which may change, a call to sysconf() can be made, which may yield more liberal results.

For getting information about a particular file, see fpathconf() or pathconf().

The following values are supported for name. First, the POSIX.1 compatible values:

The maximum length of the arguments to the exec() family of functions; the corresponding macro is ARG_MAX.


The number of simultaneous processes per user id, the corresponding macro is _POSIX_CHILD_MAX.


The number of clock ticks per second; the corresponding macro is CLK_TCK.


The maximum number of streams that a process can have open at any time. The corresponding POSIX macro is STREAM_MAX, the corresponding standard C macro is FOPEN_MAX.


The maximum number of bytes in a timezone name, the corresponding macro is TZNAME_MAX.


The maximum number of files that a process can have open at any time, the corresponding macro is _POSIX_OPEN_MAX.


This indicates whether POSIX − style job control is supported, the corresponding macro is _POSIX_JOB_CONTROL.


This indicates whether a process has a saved set-user-ID and a saved set-group-ID; the corresponding macro is _POSIX_SAVED_IDS.


indicates the year and month the POSIX.1 standard was approved in the format YYYYMML;the value 199009L indicates the most recent revision, 1990.

Next, the POSIX.2 values:

indicates the maximum obase value accepted by the bc(1) utility; the corresponding macro is BC_BASE_MAX.


indicates the maximum value of elements permitted in an array by bc(1); the corresponding macro is BC_DIM_MAX.


indicates the maximum scale value allowed by bc(1); the corresponding macro is BC_SCALE_MAX.


indicates the maximum length of a string accepted by bc(1); the corresponding macro is BC_STRING_MAX.


indicates the maximum numbers of weights that can be assigned to an entry of the LC_COLLATE order keyword in the locale definition file; the corresponding macro is COLL_WEIGHTS_MAX.


is the maximum number of expressions which can be nested within parentheses by expr(1). The corresponding macro is EXPR_NEST_MAX.


The maximum length of a utility’s input line length, either from standard input or from a file. This includes length for a trailing newline. The corresponding macro is LINE_MAX.


The maximum number of repeated occurrences of a regular expression when the interval notation \{m,n\} is used. The value of the corresponding macro is RE_DUP_MAX.


indicates the version of the POSIX.2 standard in the format of YYYYMML. The corresponding macro is POSIX2_VERSION.


indicates whether the POSIX.2 C language development facilities are supported. The corresponding macro is POSIX2_C_DEV.


indicates whether the POSIX.2 FORTRAN development utilities are supported. The corresponding macro is POSIX2_FORT_RUN.


indicates whether the POSIX.2 FORTRAN runtime utilities are supported. The corresponding macro is POSIX2_FORT_RUN.


indicates whether the POSIX.2 creation of locates via localedef(1) is supported. The corresponding macro is _POSIX2_LOCALEDEF.


indicates whether the POSIX.2 software development utilities option is supported. The corresponding macro is POSIX2_SW_DEV.

SUSv2 also lists

The size of a page (in bytes).

These values also exist, but may not be standard.

The number of pages of physical memory. Note that it is possible for the product of this value and the value of _SC_PAGE_SIZE to overflow.


The number of currently available pages of physical memory.


The value returned is the value of the system resource, 1 if a queried option is available, 0 if it is not, or −1 on error. The variable errno is not set.


POSIX.1, proposed POSIX.2


It is difficult to use ARG_MAX because it is not specified how much of the argument space for exec() is consumed by the user’s environment variables.

Some returned values may be huge; they are not suitable for allocating memory.

POSIX.2 is not yet an approved standard; the information in this manpage is subject to change.


bc(1), expr(1), locale(1), fpathconf(3), pathconf(3)