table of contents
explain_setpgrp(3) | Library Functions Manual | explain_setpgrp(3) |
NAME¶
explain_setpgrp - explain setpgrp(2) errorsSYNOPSIS¶
#include <libexplain/setpgrp.h>DESCRIPTION¶
These functions may be used to obtain explanations for errors returned by the setpgrp(2) system call. Note: the setpgrp(2) function has two implementations. The System V version has no arguments, while the BSD version has two arguments. For simplicity of implementation, the argument list seen here includes the pid and pgid arguments. The System V getpgid() semantics can be obtained by calling setpgrp(0, 0) on systems with the BSD version, and this is the API for libexplain, even on systems that do not use the BSD API.explain_setpgrp¶
const char *explain_setpgrp(pid_t pid, pid_t pgid); The explain_setpgrp function is used to obtain an explanation of an error returned by the setpgrp(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail. The errno global variable will be used to obtain the error value to be decoded.- pid
- The original pid, exactly as passed to the setpgrp(2) system call.
- pgid
- The original pgid, exactly as passed to the setpgrp(2) system call.
- Returns:
- The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.
if (setpgrp(pid, pgid) < 0)
{
fprintf(stderr, "%s\n", explain_setpgrp(pid, pgid));
exit(EXIT_FAILURE); }
explain_errno_setpgrp¶
const char *explain_errno_setpgrp(int errnum, pid_t pid, pid_t pgid); The explain_errno_setpgrp function is used to obtain an explanation of an error returned by the setpgrp(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.- errnum
- The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.
- pid
- The original pid, exactly as passed to the setpgrp(2) system call.
- pgid
- The original pgid, exactly as passed to the setpgrp(2) system call.
- Returns:
- The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.
if (setpgrp(pid, pgid) < 0)
{ int err = errno;
fprintf(stderr, "%s\n", explain_errno_setpgrp(err, pid, pgid));
exit(EXIT_FAILURE); }
explain_message_setpgrp¶
void explain_message_setpgrp(char *message, int message_size, pid_t pid, pid_t pgid); The explain_message_setpgrp function is used to obtain an explanation of an error returned by the setpgrp(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail. The errno global variable will be used to obtain the error value to be decoded.- message
- The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.
- message_size
- The size in bytes of the location in which to store the returned message.
- pid
- The original pid, exactly as passed to the setpgrp(2) system call.
- pgid
- The original pgid, exactly as passed to the setpgrp(2) system call.
if (setpgrp(pid, pgid) < 0)
{ char message[3000];explain_message_setpgrp(message, sizeof(message), pid, pgid);
fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); }
explain_message_errno_setpgrp¶
void explain_message_errno_setpgrp(char *message, int message_size, int errnum, pid_t pid, pid_t pgid); The explain_message_errno_setpgrp function is used to obtain an explanation of an error returned by the setpgrp(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.- message
- The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.
- message_size
- The size in bytes of the location in which to store the returned message.
- errnum
- The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.
- pid
- The original pid, exactly as passed to the setpgrp(2) system call.
- pgid
- The original pgid, exactly as passed to the setpgrp(2) system call.
if (setpgrp(pid, pgid) < 0)
{ int err = errno; char message[3000];explain_message_errno_setpgrp(message, sizeof(message), err, pid, pgid);
fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); }
SEE ALSO¶
- setpgrp(2)
- set process group
- explain_setpgrp_or_die(3)
- set process group and report errors