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Man Pages


Manual Reference Pages  -  EXPLAIN_SETUID (3)

NAME

explain_setuid - explain I]setuid(2) errors

CONTENTS

Synopsis
Description
See Also
Copyright

SYNOPSIS

#include <libexplain/setuid.h>

const char *explain_setuid(int uid);
const char *explain_errno_setuid(int errnum, int uid);
void explain_message_setuid(char *message, int message_size, int uid);
void explain_message_errno_setuid(char *message, int message_size, int errnum, int uid);

DESCRIPTION

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

    explain_setuid

const char *explain_setuid(int uid);

The B]explain_setuid function is used to obtain an explanation of an error returned by the I]setuid(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]uid The original uid, exactly as passed to the I]setuid(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 (setuid(uid) < 0)
{

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

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

    explain_errno_setuid

const char *explain_errno_setuid(int errnum, int uid);

The B]explain_errno_setuid function is used to obtain an explanation of an error returned by the I]setuid(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]uid The original uid, exactly as passed to the I]setuid(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 (setuid(uid) < 0)
{
    int err = errno;

fprintf(stderr, "%s\n", explain_errno_setuid(err, uid));
    exit(EXIT_FAILURE);
}

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

    explain_message_setuid

void explain_message_setuid(char *message, int message_size, int uid);

The B]explain_message_setuid function is used to obtain an explanation of an error returned by the I]setuid(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]uid The original uid, exactly as passed to the I]setuid(2) system call.
B]Example: This function is intended to be used in a fashion similar to the following example:

if (setuid(uid) < 0)
{
    char message[3000];



explain_message_setuid(message, sizeof(message), uid);


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

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

    explain_message_errno_setuid

void explain_message_errno_setuid(char *message, int message_size, int errnum, int uid);

The B]explain_message_errno_setuid function is used to obtain an explanation of an error returned by the I]setuid(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]uid The original uid, exactly as passed to the I]setuid(2) system call.
B]Example: This function is intended to be used in a fashion similar to the following example:

if (setuid(uid) < 0)
{
    int err = errno;
    char message[3000];



explain_message_errno_setuid(message, sizeof(message), err, uid);


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

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

SEE ALSO

I]setuid(2)
  set user identity
I]explain_setuid_or_die(3)
  set user identity and report errors

COPYRIGHT

libexplain version 1.3
Copyright © 2012 Peter Miller
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