sysconf()--Get System Configuration Variables
Syntax
#include <unistd.h> long sysconf(int name);
Service Program Name: QP0LLIB1
Default Public Authority: *USE
Threadsafe: Yes
The sysconf() function returns the value of a system configuration option. The configuration option to be obtained is specified by name.
Parameters
- name
- (Input) The named variable whose value is to be returned.
The value of name can be any one of the following symbols defined in the <unistd.h> header file, each corresponding to a system configuration option:
| _SC_ARG_MAX | (Not supported by the System i® product). Represents
ARG_MAX, which indicates the maximum number of bytes of arguments and
environment data that can be passed in an exec function. |
| _SC_CHILD_MAX | (Not supported by the System i product). Represents
CHILD_MAX, which indicates the maximum number of jobs that a real user ID (UID)
can have running simultaneously. |
| _SC_CLK_TCK | Represents the CLK_TCK macro, which indicates the
number of clock ticks in a second. CLK_TCK is defined in the
<time.h> header file. |
| _SC_JOB_CONTROL | (Not supported by the System i product). Represents
the _POSIX_JOB_CONTROL macro, which indicates that certain job control
operations are implemented by this version of the operating system. If
_POSIX_JOB_CONTROL is defined (in the <unistd.h> header
file), various APIs, such as setpgid(), provide more function
than when the macro is not defined. |
| _SC_NGROUPS_MAX | Represents NGROUPS_MAX, which indicates the
maximum number of supplementary group IDs (GIDs) that can be associated with a
job. |
| _SC_OPEN_MAX | Represents OPEN_MAX, which indicates the maximum
number of files that a single job can have open at one time. |
| _SC_PAGESIZE | Represents the system hardware page size. The
symbol _SC_PAGESIZE is defined as the decimal value 11. |
| _SC_PAGE_SIZE | Represents the system hardware page size. The
symbol _SC_PAGE_SIZE is defined as the decimal value 12. |
| _SC_SAVED_IDS | (Not supported by the System i product). Represents
the _POSIX_SAVED_IDS macro, which indicates that this POSIX implementation has
a saved set UID and a saved set GID. If the macro exists, it is defined in the
<unistd.h> header file. This symbol affects the behavior
of such functions as setuid() and
setgid(). |
| _SC_STREAM_MAX | Represents the STREAM_MAX macro, which indicates
the maximum number of streams that a job can have open at one time. The macro
is defined in the <limits.h> header file. |
| _SC_TZNAME_MAX | (Not supported by the System i product). Represents
the TZNAME_MAX macro, which indicates the maximum length of the name of a time
zone. If the macro exists, it is defined in the
<limits.h> header file. |
| _SC_VERSION | (Not supported by the System i product). Represents
the _POSIX_VERSION macro, which indicates the version of the POSIX.1 standard
that the system conforms to. If the macro exists, it is defined in the
<unistd.h> header file. |
| _SC_CCSID | Represents the default coded character set identifier (CCSID) used internally for integrated file system path names. A CCSID uniquely identifies the coded graphic character representation of a path name and includes such information as the character set and code page identifier. The symbol _SC_CCSID is defined as the decimal value 10. |
Authorities
No authorization is required.
Return Value
| value | sysconf() was successful. The value associated with the specified option is returned. |
| -1 | One of the following has occurred:
|
Error Conditions
If sysconf() is not successful, errno usually indicates one of the following errors. Under some conditions, errno could indicate an error other than those listed here.
| Error condition | Additional information |
|---|---|
| [EBADFID] | |
| [EINVAL] |
Error Messages
The following messages may be sent from this function:
| Message ID | Error Message Text |
|---|---|
| CPE3418 E | Possible APAR condition or hardware failure. |
| CPF3CF2 E | Error(s) occurred during running of &1 API. |
Related Information
- The <unistd.h> file (see Header Files for UNIX®-Type Functions)
Example
The following example determines the value of OPEN_MAX.
Note: By using the code examples, you agree to the terms of the Code license and disclaimer information.
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
main() {
long result;
errno = 0;
puts("examining OPEN_MAX limit");
if ((result = sysconf(_SC_OPEN_MAX)) == -1)
if (errno == 0)
puts("OPEN_MAX is not supported.");
else perror("sysconf() error");
else
printf("OPEN_MAX is %ld\n", result);
}
Output:
examining OPEN_MAX limit OPEN_MAX is 200
API introduced: V3R1