libexplain/setreuid.h File Reference

explain setreuid(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_setreuid_or_die (uid_t ruid, uid_t euid)
int	explain_setreuid_on_error (uid_t ruid, uid_t euid)
const char *	explain_setreuid (uid_t ruid, uid_t euid) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_setreuid (int errnum, uid_t ruid, uid_t euid) LIBEXPLAIN_WARN_UNUSED_RESULT
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)

---

Detailed Description

explain setreuid(2) errors

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

Definition in file setreuid.h.

---

Function Documentation

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(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.
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 function.

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(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.
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 function.

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(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.
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 function.

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.

Parameters:

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 function.

int explain_setreuid_on_error	(	uid_t	ruid,
		uid_t	euid
	)

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

Parameters:

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

Returns:

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

Example:

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

 if (explain_setreuid_on_error(ruid, euid) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

void explain_setreuid_or_die	(	uid_t	ruid,
		uid_t	euid
	)

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

Parameters:

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

Returns:

This function only returns on success, see setreuid(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_setreuid_or_die(ruid, euid);