HP C
Run-Time Library Reference Manual for OpenVMS Systems
Previous Contents Index

setbuf

Associates a new buffer with an input or output file and potentially modifies the buffering behavior.

Format

#include <stdio.h>

void setbuf (FILE *file_ptr, char *buffer);

Arguments

file_ptr

A file pointer.

buffer

A pointer to a character array or a NULL pointer.

Description

You can use the setbuf function after the specified file is opened but before any I/O operations are performed.

If buffer is a NULL pointer, then the call is equivalent to a call to setvbuf with the same file_ptr, a NULL buffer pointer, a buffering type of _IONBF (no buffering), and a buffer size of 0.

If buffer is not a NULL pointer, then the call is equivalent to a call to setvbuf with the same file_ptr, the same buffer pointer, a buffering type of _IOFBF, and a buffer size given by the value BUFSIZ (defined in <stdio.h> ). Therefore, use BUFSIZ to allocate the buffer argument used in the call to setbuf . For example: 


#include <stdio.h> 
   .
   .
   .
char my_buf[BUFSIZ]; 
   .
   .
   .
setbuf(stdout, my_buf); 
   .
   .
   .

User programs must not depend on the contents of buffer once I/O has been performed on the stream. The HP C RTL might or might not use buffer for any given I/O operation.

The setbuf function originally allowed programmers to substitute larger buffers in place of the system default buffers in obsolete versions of UNIX. The large default buffer sizes in modern implementations of C make the use of this function unnecessary most of the time. The setbuf function is retained in the ANSI C standard for compatibility with old programs. New programs should use setvbuf instead, because it allows the programmer to bind the buffer size at run time instead of compile time, and it returns a result value that can be tested.

setenv

Inserts or resets the environment variable specified by name in the current environment list.

Format

#include <stdlib.h>

int setenv (const char *name, const char *value, int overwrite);

Arguments

name

A variable name in the environment variable list.

value

The value for the environment variable.

overwrite

A value of 0 or 1 indicating whether to reset the environment variable, if it exists.

Description

The setenv function inserts or resets the environment variable name in the current environment list. If the variable name does not exist in the list, it is inserted with the value argument. If the variable does exist, the overwrite argument is tested. When the overwrite argument value is:

Note
Do not use the setenv , getenv , and putenv functions to manipulate symbols and logicals. Instead, use the OpenVMS library calls lib$set_logical , lib$get_logical , lib$set_symbol , and lib$get_symbol . The * env functions deliberately provide UNIX behavior, and are not a substitute for these OpenVMS runtime library calls.

OpenVMS DCL symbols, not logical names, are the closest analog to environment variables on UNIX systems. While getenv is a mechanism to retrieve either a logical name or a symbol, it maintains an internal cache of values for use with setenv and subsequent getenv calls. The setenv function does not write or create DCL symbols or OpenVMS logical names.

This is consistent with UNIX behavior. On UNIX systems, setenv does not change or create any symbols that will be visible in the shell after the program exits.

Return Values

0 Indicates success.
- 1 Indicates an error. errno is set to ENOMEM---Not enough memory available to expand the environment list.

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.

This function requires that long (32-bit) UID/GID support be enabled. See Section 1.5.8 for more information.

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:

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
The C RTL provides nonstandard decc$setjmp and decc$fast_longjmp functions for Alpha and I64 systems. 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:

Return Values

See the Description section.  

setkey

Sets an encoding key for use by the encrypt function.

Format

#include <unistd.h>

#include <stdlib.h>

void setkey (const char *key;)

Argument

key

A character array of length 64 containing 0s and 1s.

Description

The argument of setkey is a character array of length 64 containing only the characters with numerical value 0 and 1. If this string is divided into groups of 8, the low-order bit in each group is ignored, leading to a 56-bit key which is set into the machine.

No value is returned.

See also crypt and encrypt .

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:

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:

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

Previous Next Contents Index