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HP OpenVMS Systems

C Programming Language

HP C

HP C
Run-Time Library Reference Manual for OpenVMS Systems

Contents

Index

seteuid (ALPHA, I64)

Sets the process's effective user ID.

Format

#include <unistd.h>
int seteuid (uid_t euid);

Argument

euid
The value to which you want the effective user ID set.

Description

If the process has the IMPERSONATE privilege, the seteuid function sets the process's effective user ID.
An unprivileged process can set the effective user ID only if the euid argument is equal to either the real, effective, or saved user ID of the process.

Return Values

0 Successful completion.

- 1 Indicates an error. The function sets errno to one of the following values:

EINVAL -- The value of the euid argument is invalid and not supported.
EPERM -- The process does not have the IMPERSONATE privilege, and euid does not match the real user ID or the saved set-user-ID.

setgid

With POSIX IDs disabled, setgid is implemented for program portability and serves no function. It returns 0 (to indicate success).
With POSIX IDs enabled, setgid sets the group IDs.

Format

#include <types.h>
#include <unistd.h>
int setgid (__gid_t gid); (_DECC_V4_SOURCE)
int setgid (gid_t gid); (NOT _DECC_V4_SOURCE)

Argument

gid
The value to which you want the group IDs set.

Description

The setgid function can be used with POSIX style identifiers enabled or disabled.
POSIX style IDs are supported on OpenVMS Version 7.3-2 and higher.
With POSIX IDs disabled, the setgid function is implemented for program portability and serves no function. It returns 0 (to indicate success).
With POSIX style IDs enabled:

If the process has the IMPERSONATE privilege, the setgid function sets the real group ID, effective group ID, and the saved set-group-ID to gid.
If the process does not have appropriate privileges but gid is equal to the real group ID or to the saved set-group-ID, then the setgid function sets the effective group ID to gid. The real group ID and saved set-group-ID remain unchanged.
Any supplementary group IDs of the calling process remain unchanged.

To enable/disable POSIX style IDs, see Section 1.7.

Return Values

0 Successful completion.

- 1 Indicates an error. The function sets errno to one of the following values:

EINVAL -- The value of the gid argument is invalid and not supported by the implementation.
EPERM -- The process does not have appropriate privileges and gid does not match the real group ID or the saved set-group-ID.

setgrent (ALPHA, I64)

Rewinds the group database.

Format

#include <grp.h>
void setgrent (void);

Description

The setgrent function effectively rewinds the group database to allow repeated searches.
This function is always successful. No value is returned, and errno is not set.

setitimer

Sets the value of interval timers.

Format

#include <time.h>
int setitimer (int which, struct itimerval *value, struct itimerval *ovalue);

Arguments

which
The type of interval timer. The HP C RTL only supports ITIMER_REAL.
value
A pointer to an itimerval structure whose members specify a timer interval and the time left to the end of the interval.
ovalue
A pointer to an itimerval structure whose members specify a current timer interval and the time left to the end of the interval.

Description

The setitimer function sets the timer specified by which to the value specified by value, returning the previous value of the timer if ovalue is nonzero.
A timer value is defined by the itimerval structure:
struct itimerval { struct timeval it_interval; struct timeval it_value; };
The value of the itimerval structure members are: as follows

itimerval Member Value Meaning

it_interval = 0 Disables a timer after its next expiration (assumes it_value is nonzero).

it_interval = nonzero Specifies a value used in reloading it_value when the timer expires.

it_value = 0 Disables a timer.

it_value = nonzero Indicates the time to the next timer expiration.

Time values smaller than the resolution of the system clock are rounded up to this resolution.
The getitimer function provides one interval timer, defined in the <time.h> header file as ITIMER_REAL. This timer decrements in real time. When the timer expires, it delivers a SIGALARM signal.

Note
The interaction between setitimer and any of alarm , sleep , or usleep is unspecified.

Return Values

0 Indicates success.

- 1 An error occurred; errno is set to indicate the error.

setjmp

Provides a way to transfer control from a nested series of function invocations back to a predefined point without returning normally. It does not use a series of return statements. The setjmp function saves the context of the calling function in an environment buffer.

Format

#include <setjmp.h>
int setjmp (jmp_buf env);

Argument

env
The environment buffer, which must be an array of integers long enough to hold the register context of the calling function. The type jmp_buf is defined in the <setjmp.h> header file. The contents of the general-purpose registers, including the program counter (PC), are stored in the buffer.

Description

When setjmp is first called, it returns the value 0. If longjmp is then called, naming the same environment as the call to setjmp , control is returned to the setjmp call as if it had returned normally a second time. The return value of setjmp in this second return is the value supplied by you in the longjmp call. To preserve the true value of setjmp , the function calling setjmp must not be called again until the associated longjmp is called.
The setjmp function preserves the hardware general-purpose registers, and the longjmp function restores them. After a longjmp , all variables have their values as of the time of the longjmp except for local automatic variables not marked volatile . These variables have indeterminate values.
The setjmp and longjmp functions rely on the OpenVMS condition-handling facility to effect a nonlocal goto with a signal handler. The longjmp function is implemented by generating a HP C RTL specified signal that allows the OpenVMS condition-handling facility to unwind back to the desired destination.
The HP C RTL must be in control of signal handling for any HP C image. For HP C to be in control of signal handling, you must establish all exception handlers through a call to the VAXC$ESTABLISH function. See Section 4.2.5 and the VAXC$ESTABLISH function for more information.

Note
There are Alpha specific, nonstandard decc$setjmp and decc$fast_longjmp functions. To use these nonstandard functions instead of the standard ones, a program must be compiled with __FAST_SETJMP or __UNIX_SETJMP macros defined.

Unlike the standard longjmp function, the decc$fast_longjmp function does not convert its second argument from 0 to 1. After a call to decc$fast_longjmp , a corresponding setjmp function returns with the exact value of the second argument specified in the decc$fast_longjmp call.

Restrictions

You cannot invoke the longjmp function from an OpenVMS condition handler. However, you may invoke longjmp from a signal handler that has been established for any signal supported by the HP C RTL, subject to the following nesting restrictions:

The longjmp function will not work if you invoke it from nested signal handlers. The result of the longjmp function, when invoked from a signal handler that has been entered as a result of an exception generated in another signal handler, is undefined.
Do not invoke the setjmp function from a signal handler unless the associated longjmp is to be issued before the handling of that signal is completed.
Do not invoke the longjmp function from within an exit handler (established with atexit or SYS$DCLEXH). Exit handlers are invoked after image tear-down, so the destination address of the longjmp no longer exists.
Invoking longjmp from within a signal handler to return to the main thread of execution might leave your program in an inconsistent state. Possible side effects include the inability to perform I/O or to receive any more UNIX signals. Use siglongjmp instead.

Return Values

See the Description section.

setlocale

Selects the appropriate portion of the program's locale as specified by the category and locale arguments. You can use this function to change or query one category or the program's entire current locale.

Format

#include <locale.h>
char *setlocale (int category, const char *locale);

Arguments

category
The name of the category. Specify LC_ALL to change or query the entire locale. Other valid category names are:

LC_COLLATE
LC_CTYPE
LC_MESSAGES
LC_MONETARY
LC_NUMERIC
LC_TIME

locale
Pointer to a string that specifies the locale.

Description

The setlocale function sets or queries the appropriate portion of the program's locale as specified by the category and locale arguments. Specifying LC_ALL for the category argument names the entire locale; specifying the other values name only a portion of the program's locale.
The locale argument points to a character string that identifies the locale to be used. This argument can be one of the following:
Name of the public locale
Specifies the public locale in the following format:
language_country.codeset[@modifier]
The function searches for the public locale binary file in the location defined by the logical name SYS$I18N_LOCALE. The file type defaults to .LOCALE. The period (.) and at-sign (@) characters in the name are replaced by an underscore (_).
For example, if the specified name is "zh_CN.dechanzi@radical", the function searches for the SYS$I18N_LOCALE:ZH_CN_DECHANZI_RADICAL.LOCALE binary locale file.
A file specification
Specifies the binary locale file. It can be any valid file specification. If either the device or directory is omitted, the function first applies the current caller's device and directory as defaults for any missing component. If the file is not found, the function applies the device and directory defined by the SYS$I18N_LOCALE logical name as defaults. The file type defaults to .LOCALE.
No wildcards are allowed. The binary locale file cannot reside on a remote node.
"C"
Specifies the C locale. If a program does not call setlocale , the C locale is the default.
"POSIX"
This is the same as the C locale.
""
Specifies that the locale is initialized from the setting of the international environment logical names. The function checks the following logical names in the order shown until it finds a logical that is defined:

LC_ALL
Logical names corresponding to the category. For example, if LC_NUMERIC is specified as the category, then the first logical name that setlocale checks is LC_NUMERIC.
LANG
SYS$LC_ALL
The system default for the category, which is defined by the SYS$LC_* logical names. For example, the default for the LC_NUMERIC category is defined by the SYS$LC_NUMERIC logical name.
SYS$LANG
If none of the logical names is defined, the C locale is used as the default. The SYS$LC_* logical names are set up at the system startup time.

Like the locale argument, the equivalence name of the international environment logical name can be either the name of the public locale or the file specification. The setlocale function treats this equivalence name as if it were specified as the locale argument.
NULL
Causes setlocale to query the current locale. The function returns a pointer to a string describing the portion of the program's locale associated with category. Specifying the LC_ALL category returns the string describing the entire locale. The locale is not changed.
The string returned from the previous call to setlocale
Causes the function to restore the portion of the program's locale associated with category. If the string contains the description of the entire locale, the part of the string corresponding to category is used. If the string describes the portion of the program's locale for a single category, this locale is used. For example, this means that you can use the string returned from the call setlocale with the LC_COLLATE category to set the same locale for the LC_MESSAGES category.
If the specified locale is available, then setlocale returns a pointer to the string that describes the portion of the program's locale associated with category. For the LC_ALL category, the returned string describes the entire program's locale. If an error occurs, a NULL pointer is returned and the program's locale is not changed.
Subsequent calls to setlocale overwrite the returned string. If that part of the locale needs to be restored, the program should save the string. The calling program should make no assumptions about the format or length of the returned string.

Return Values

x Pointer to a string describing the locale.

NULL Indicates an error occurred; errno is set.

Example

#include <errno.h> 
#include <stdio.h> 
#include <locale.h> 
 
/* This program calls setlocale() three times. The second call  */ 
/* is for a nonexistent locale. The third call is for an        */ 
/* existing file that is not a locale file.                     */ 
 
main() 
{ 
    char *ret_str; 
 
    errno = 0; 
    printf("setlocale (LC_ALL, \"POSIX\")"); 
    ret_str = (char *) setlocale(LC_ALL, "POSIX"); 
 
    if (ret_str == NULL) 
        perror("setlocale error"); 
    else 
        printf(" call was successful\n"); 
                                            
    errno = 0; 
    printf("\n\nsetlocale (LC_ALL, \"junk.junk_codeset\")"); 
    ret_str = (char *) setlocale(LC_ALL, "junk.junk_codeset"); 
 
    if (ret_str == NULL) 
        perror(" returned error"); 
    else 
        printf(" call was successful\n"); 
 
    errno = 0; 
    printf("\n\nsetlocale (LC_ALL, \"sys$login:login.com\")"); 
    ret_str = (char *) setlocale(LC_ALL, "sys$login:login.com"); 
 
    if (ret_str == NULL) 
        perror(" returned error"); 
    else 
        printf(" call was successful\n"); 
}

Running the example program produces the following result:

setlocale (LC_ALL, "POSIX") call was successful 
 
setlocale (LC_ALL, "junk.junk_codeset") 
returned error: no such file or directory 
 
setlocale (LC_ALL, "sys$login:login.com") 
returned error: nontranslatable vms error code: 0x35C07C 
%c-f-localebad, not a locale file

setpgid (ALPHA, I64)

Sets the process group ID for job control.

Format

#include <unistd.h>
int setpgid (pid_t pid, pid_t pgid);

Arguments

pid
The process ID for which the process group ID is to be set.
pgid
The value to which the process group ID is set.

Description

The setpgid function is used either to join an existing process group or create a new process group within the session of the calling process. The process group ID of a session leader will not change.
Upon successful completion, the process group ID of the process with a process ID of pid is set to pgid. As a special case, if pid is 0, the process ID of the calling process is used. Also, if pgid is 0, the process group ID of the indicated process is used.

Return Values

0 Successful completion.

- 1 Indicates an error. The function sets errno to one of the following values:

EACCES -- The value of the pid argument matches the process ID of a child process of the calling process and the child process has successfully executed one of the exec functions.
EINVAL -- The value of the pgid argument is less than 0, or is not a value supported by the implementation.
EPERM -- The process indicated by the pid argument is a session leader. The value of the pid argument matches the process ID of a child process of the calling process, and the child process is not in the same session as the calling process. The value of the pgid argument is valid but does not match the process ID of the process indicated by the pid argument, and there is no process with a process group ID that matches the value of the pgid argument in the same session as the calling process.
ESRCH -- The value of the pid argument does not match the process ID of the calling process or of a child process of the calling process.

setpgrp (ALPHA, I64)

Sets the process group ID.

Format

#include <unistd.h>
pid_t setpgrp (void);

Description

If the calling process is not already a session leader, setpgrp sets the process group ID of the calling process to the process ID of the calling process. If setpgrp creates a new session, then the new session has no controlling terminal.
The setpgrp function has no effect when the calling process is a session leader.

Return Value

x The process group ID of the calling process.

Contents

Index

HP OpenVMS Systems

HP CRun-Time Library Reference Manual for OpenVMS Systems

seteuid (ALPHA, I64)

Format

Argument

euid

Description

Return Values

setgid

Format

Argument

gid

Description

Return Values

setgrent (ALPHA, I64)

Format

Description

setitimer

Format

Arguments

which

value

ovalue

Description

Return Values

setjmp

Format

Argument

env

Description

Restrictions

Return Values

setlocale

Format

Arguments

category

locale

Description

Return Values

Example

setpgid (ALPHA, I64)

Format

Arguments

pid

pgid

Description

Return Values

setpgrp (ALPHA, I64)

Format

Description

Return Value

HP C
Run-Time Library Reference Manual for OpenVMS Systems