explain_setpgid man page

explain_setpgid — explain setpgid(2) errors

Synopsis

#include <libexplain/setpgid.h>

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

Description

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

explain_setpgid

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.

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(3) function.

explain_errno_setpgid

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(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 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(3) function.

explain_message_setpgid

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(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 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(3) function.

explain_message_errno_setpgid

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(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 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(3) function.

See Also

setpgid(2)
set process group
explain_setpgid_or_die(3)
set process group and report errors

Referenced By

explain(3), explain_setpgid_or_die(3).