explain_setreuid(3)

NAME
explain_setreuid - explain setreuid(2) errors

SYNOPSIS
#include <libexplain/setreuid.h>

const char *explain_setreuid(uid_t ruid, uid_t euid);
const char *explain_errno_setreuid(int errnum, uid_t ruid, uid_t euid);
void explain_message_setreuid(char *message, int message_size, uid_t ruid, uid_t euid);
void explain_message_errno_setreuid(char *message, int message_size, int errnum, uid_t ruid, uid_t euid);

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

  explain_setreuid
const char *explain_setreuid(uid_t ruid, uid_t euid);

The explain_setreuid function is used to obtain an explanation of an error returned by the setreuid(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.

ruid
    The original ruid, exactly as passed to the setreuid(2) system call.

euid
    The original euid, exactly as passed to the setreuid(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 (setreuid(ruid, euid) < 0)
    {
    fprintf(stderr, "%s\n", explain_setreuid(ruid, euid));
        exit(EXIT_FAILURE);
    }

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

  explain_errno_setreuid
const char *explain_errno_setreuid(int errnum, uid_t ruid, uid_t euid);

The explain_errno_setreuid function is used to obtain an explanation of an error returned by the setreuid(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.

ruid
    The original ruid, exactly as passed to the setreuid(2) system call.

euid
    The original euid, exactly as passed to the setreuid(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 (setreuid(ruid, euid) < 0)
    {
        int err = errno;
    fprintf(stderr, "%s\n", explain_errno_setreuid(err, ruid, euid));
        exit(EXIT_FAILURE);
    }

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

  explain_message_setreuid
void explain_message_setreuid(char *message, int message_size, uid_t ruid, uid_t euid);

The explain_message_setreuid function is used to obtain an explanation of an error returned by the setreuid(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.

ruid
    The original ruid, exactly as passed to the setreuid(2) system call.

euid
    The original euid, exactly as passed to the setreuid(2) system call.

Example: This function is intended to be used in a fashion similar to the following example:
    if (setreuid(ruid, euid) < 0)
    {
        char message[3000];
    explain_message_setreuid(message, sizeof(message), ruid, euid);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

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

  explain_message_errno_setreuid
void explain_message_errno_setreuid(char *message, int message_size, int errnum, uid_t ruid, uid_t euid);

The explain_message_errno_setreuid function is used to obtain an explanation of an error returned by the setreuid(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.

ruid
    The original ruid, exactly as passed to the setreuid(2) system call.

euid
    The original euid, exactly as passed to the setreuid(2) system call.

Example: This function is intended to be used in a fashion similar to the following example:
    if (setreuid(ruid, euid) < 0)
    {
        int err = errno;
        char message[3000];
    explain_message_errno_setreuid(message, sizeof(message), err, ruid, euid);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

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

SEE ALSO

setreuid(2)
    set the real and effective user ID

explain_setreuid_or_die(3)
    set the real and effective user ID and report errors

COPYRIGHT
libexplain version
Copyright (C) 2012 Peter Miller