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Man Pages


Manual Reference Pages  -  EXPLAIN_SETPGRP (3)

NAME

explain_setpgrp - explain I]setpgrp(2) errors

CONTENTS

Synopsis
Description
See Also
Copyright

SYNOPSIS

#include <libexplain/setpgrp.h>

const char *explain_setpgrp(pid_t pid, pid_t pgid);
const char *explain_errno_setpgrp(int errnum, pid_t pid, pid_t pgid);
void explain_message_setpgrp(char *message, int message_size, pid_t pid, pid_t pgid);
void explain_message_errno_setpgrp(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 I]setpgrp(2) system call.

B]Note: the I]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 I]pid and I]pgid arguments.

The System V CW]getpgid() semantics can be obtained by calling CW]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 B]explain_setpgrp function is used to obtain an explanation of an error returned by the I]setpgrp(2) system call. The least the message will contain is the value of CW]strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The I]errno global variable will be used to obtain the error value to be decoded.
I]pid The original pid, exactly as passed to the I]setpgrp(2) system call.
I]pgid The original pgid, exactly as passed to the I]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.
B]Note: This function is B]not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

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

if (setpgrp(pid, pgid) < 0)
{

fprintf(stderr, "%s\n", explain_setpgrp(pid, pgid));
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the I]explain_setpgrp_or_die(3) function.

    explain_errno_setpgrp

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

The B]explain_errno_setpgrp function is used to obtain an explanation of an error returned by the I]setpgrp(2) system call. The least the message will contain is the value of CW]strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.
I]errnum The error value to be decoded, usually obtained from the I]errno global variable just before this function is called. This is necessary if you need to call B]any code between the system call to be explained and this function, because many libc functions will alter the value of I]errno.
I]pid The original pid, exactly as passed to the I]setpgrp(2) system call.
I]pgid The original pgid, exactly as passed to the I]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.
B]Note: This function is B]not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

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

if (setpgrp(pid, pgid) < 0)
{
    int err = errno;

fprintf(stderr, "%s\n", explain_errno_setpgrp(err, pid, pgid));
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the I]explain_setpgrp_or_die(3) function.

    explain_message_setpgrp

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

The B]explain_message_setpgrp function is used to obtain an explanation of an error returned by the I]setpgrp(2) system call. The least the message will contain is the value of CW]strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The I]errno global variable will be used to obtain the error value to be decoded.
I]message
  The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.
I]message_size
  The size in bytes of the location in which to store the returned message.
I]pid The original pid, exactly as passed to the I]setpgrp(2) system call.
I]pgid The original pgid, exactly as passed to the I]setpgrp(2) system call.
B]Example: This function is intended to be used in a fashion similar to the following example:

if (setpgrp(pid, pgid) < 0)
{
    char message[3000];



explain_message_setpgrp(message, sizeof(message), pid, pgid);


    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the I]explain_setpgrp_or_die(3) function.

    explain_message_errno_setpgrp

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

The B]explain_message_errno_setpgrp function is used to obtain an explanation of an error returned by the I]setpgrp(2) system call. The least the message will contain is the value of CW]strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.
I]message
  The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.
I]message_size
  The size in bytes of the location in which to store the returned message.
I]errnum The error value to be decoded, usually obtained from the I]errno global variable just before this function is called. This is necessary if you need to call B]any code between the system call to be explained and this function, because many libc functions will alter the value of I]errno.
I]pid The original pid, exactly as passed to the I]setpgrp(2) system call.
I]pgid The original pgid, exactly as passed to the I]setpgrp(2) system call.
B]Example: This function is intended to be used in a fashion similar to the following example:

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);
}

The above code example is available pre-packaged as the I]explain_setpgrp_or_die(3) function.

SEE ALSO

I]setpgrp(2)
  set process group
I]explain_setpgrp_or_die(3)
  set process group and report errors

COPYRIGHT

libexplain version 1.3
Copyright © 2011 Peter Miller
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