explain_getresuid man page

explain_getresuid — explain getresuid(2) errors

Synopsis

#include <libexplain/getresuid.h>

const char *explain_getresuid(uid_t *ruid, uid_t *euid, uid_t *suid);
const char *explain_errno_getresuid(int errnum, uid_t *ruid, uid_t *euid, uid_t *suid);
void explain_message_getresuid(char *message, int message_size, uid_t *ruid, uid_t *euid, uid_t *suid);
void explain_message_errno_getresuid(char *message, int message_size, int errnum, uid_t *ruid, uid_t *euid, uid_t *suid);

Description

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

explain_getresuid

const char *explain_getresuid(uid_t *ruid, uid_t *euid, uid_t *suid);

The explain_getresuid function is used to obtain an explanation of an error returned by the getresuid(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 getresuid(2) system call.
euid
The original euid, exactly as passed to the getresuid(2) system call.
suid
The original suid, exactly as passed to the getresuid(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 (getresuid(ruid, euid, suid) < 0)

{

fprintf(stderr, "%s\n", explain_getresuid(ruid, euid, suid));

    exit(EXIT_FAILURE);
}

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

explain_errno_getresuid

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

The explain_errno_getresuid function is used to obtain an explanation of an error returned by the getresuid(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 getresuid(2) system call.
euid
The original euid, exactly as passed to the getresuid(2) system call.
suid
The original suid, exactly as passed to the getresuid(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 (getresuid(ruid, euid, suid) < 0)

{
    int err = errno;

fprintf(stderr, "%s\n", explain_errno_getresuid(err, ruid, euid, suid));

    exit(EXIT_FAILURE);
}

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

explain_message_getresuid

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

The explain_message_getresuid function is used to obtain an explanation of an error returned by the getresuid(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 getresuid(2) system call.
euid
The original euid, exactly as passed to the getresuid(2) system call.
suid
The original suid, exactly as passed to the getresuid(2) system call.

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

if (getresuid(ruid, euid, suid) < 0)

{
    char message[3000];

explain_message_getresuid(message, sizeof(message), ruid, euid, suid);

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

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

explain_message_errno_getresuid

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

The explain_message_errno_getresuid function is used to obtain an explanation of an error returned by the getresuid(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 getresuid(2) system call.
euid
The original euid, exactly as passed to the getresuid(2) system call.
suid
The original suid, exactly as passed to the getresuid(2) system call.

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

if (getresuid(ruid, euid, suid) < 0)

{
    int err = errno;
    char message[3000];

explain_message_errno_getresuid(message, sizeof(message), err, ruid, euid, suid);

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

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

See Also

getresuid(2)
get real, effective and saved user IDs
explain_getresuid_or_die(3)
get real, effective and saved user IDs and report errors

Referenced By

explain(3), explain_getresuid_or_die(3).