libexplain/setpgid.h File Reference

explain setpgid(2) errors More...

#include <libexplain/gcc_attributes.h>
#include <libexplain/large_file_support.h>
#include <unistd.h>

Go to the source code of this file.

Functions
void	explain_setpgid_or_die (pid_t pid, pid_t pgid)
int	explain_setpgid_on_error (pid_t pid, pid_t pgid)
const char *	explain_setpgid (pid_t pid, pid_t pgid) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_setpgid (int errnum, pid_t pid, pid_t pgid) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_setpgid (char *message, int message_size, pid_t pid, pid_t pgid)
void	explain_message_errno_setpgid (char *message, int message_size, int errnum, pid_t pid, pid_t pgid)

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Detailed Description

explain setpgid(2) errors

These functions may be used to obtain explanations for errors returned by the setpgid(2) system call.

Definition in file setpgid.h.

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Function Documentation

const char* explain_errno_setpgid	(	int	errnum,
		pid_t	pid,
		pid_t	pgid
	)

The explain_errno_setpgid function is used to obtain an explanation of an error returned by the setpgid(2) system call. The least the message will contain is the value of strerror(errnum), but usually it will do much better, and indicate the underlying cause in more detail.

Parameters:

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 setpgid(2) system call.
pgid	The original pgid, exactly as passed to the setpgid(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.

Note:

This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

Example:

This function is intended to be used in a fashion similar to the following example:

 if (setpgid(pid, pgid) < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_setpgid(err, pid, pgid));
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_setpgid_or_die function.

void explain_message_errno_setpgid	(	char *	message,
		int	message_size,
		int	errnum,
		pid_t	pid,
		pid_t	pgid
	)

The explain_message_errno_setpgid function is used to obtain an explanation of an error returned by the setpgid(2) system call. The least the message will contain is the value of strerror(errnum), but usually it will do much better, and indicate the underlying cause in more detail.

Parameters:

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 setpgid(2) system call.
pgid	The original pgid, exactly as passed to the setpgid(2) system call.

Example:

This function is intended to be used in a fashion similar to the following example:

 if (setpgid(pid, pgid) < 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_setpgid(message, sizeof(message), err, pid, pgid);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_setpgid_or_die function.

void explain_message_setpgid	(	char *	message,
		int	message_size,
		pid_t	pid,
		pid_t	pgid
	)

The explain_message_setpgid function is used to obtain an explanation of an error returned by the setpgid(2) system call. The least the message will contain is the value of strerror(errnum), 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.

Parameters:

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 setpgid(2) system call.
pgid	The original pgid, exactly as passed to the setpgid(2) system call.

Example:

This function is intended to be used in a fashion similar to the following example:

 if (setpgid(pid, pgid) < 0)
 {
     char message[3000];
     explain_message_setpgid(message, sizeof(message), pid, pgid);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_setpgid_or_die function.

const char* explain_setpgid	(	pid_t	pid,
		pid_t	pgid
	)

The explain_setpgid function is used to obtain an explanation of an error returned by the setpgid(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.

Parameters:

pid	The original pid, exactly as passed to the setpgid(2) system call.
pgid	The original pgid, exactly as passed to the setpgid(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.

Note:

This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

Example:

This function is intended to be used in a fashion similar to the following example:

 if (setpgid(pid, pgid) < 0)
 {
     fprintf(stderr, "%s\n", explain_setpgid(pid, pgid));
     exit(EXIT_FAILURE);
 }

The above code example is available pre\-packaged as the explain_setpgid_or_die function.

int explain_setpgid_on_error	(	pid_t	pid,
		pid_t	pgid
	)

The explain_setpgid_on_error function is used to call the setpgid(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_setpgid(3) function.

Parameters:

pid	The pid, exactly as to be passed to the setpgid(2) system call.
pgid	The pgid, exactly as to be passed to the setpgid(2) system call.

Returns:

The value returned by the wrapped setpgid(2) system call.

Example:

This function is intended to be used in a fashion similar to the following example:

 if (explain_setpgid_on_error(pid, pgid) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

void explain_setpgid_or_die	(	pid_t	pid,
		pid_t	pgid
	)

The explain_setpgid_or_die function is used to call the setpgid(2) system call. On failure an explanation will be printed to stderr, obtained from the explain_setpgid(3) function, and then the process terminates by calling exit(EXIT_FAILURE).

Parameters:

pid	The pid, exactly as to be passed to the setpgid(2) system call.
pgid	The pgid, exactly as to be passed to the setpgid(2) system call.

Returns:

This function only returns on success, see setpgid(2) for more information. On failure, prints an explanation and exits, it does not return.

Example:

This function is intended to be used in a fashion similar to the following example:

 explain_setpgid_or_die(pid, pgid);