explain_fchownat man page

explain_fchownat — explain fchownat(2) errors

Synopsis

#include <libexplain/fchownat.h>

const char *explain_fchownat(int dirfd, const char *pathname, int owner, int group, int flags);
const char *explain_errno_fchownat(int errnum, int dirfd, const char *pathname, int owner, int group, int flags);
void explain_message_fchownat(char *message, int message_size, int dirfd, const char *pathname, int owner, int group, int flags);
void explain_message_errno_fchownat(char *message, int message_size, int errnum, int dirfd, const char *pathname, int owner, int group, int flags);

Description

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

explain_fchownat

const char *explain_fchownat(int dirfd, const char *pathname, int owner, int group, int flags);

The explain_fchownat function is used to obtain an explanation of an error returned by the fchownat(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.

dirfd
The original dirfd, exactly as passed to the fchownat(2) system call.
pathname
The original pathname, exactly as passed to the fchownat(2) system call.
owner
The original owner, exactly as passed to the fchownat(2) system call.
group
The original group, exactly as passed to the fchownat(2) system call.
flags
The original flags, exactly as passed to the fchownat(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 (fchownat(dirfd, pathname, owner, group, flags) < 0)

{

fprintf(stderr, "%s\n", explain_fchownat(dirfd, pathname, owner, group, flags));

    exit(EXIT_FAILURE);
}

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

explain_errno_fchownat

const char *explain_errno_fchownat(int errnum, int dirfd, const char *pathname, int owner, int group, int flags);

The explain_errno_fchownat function is used to obtain an explanation of an error returned by the fchownat(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.
dirfd
The original dirfd, exactly as passed to the fchownat(2) system call.
pathname
The original pathname, exactly as passed to the fchownat(2) system call.
owner
The original owner, exactly as passed to the fchownat(2) system call.
group
The original group, exactly as passed to the fchownat(2) system call.
flags
The original flags, exactly as passed to the fchownat(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 (fchownat(dirfd, pathname, owner, group, flags) < 0)

{
    int err = errno;

fprintf(stderr, "%s\n", explain_errno_fchownat(err, dirfd, pathname, owner, group, flags));

    exit(EXIT_FAILURE);
}

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

explain_message_fchownat

void explain_message_fchownat(char *message, int message_size, int dirfd, const char *pathname, int owner, int group, int flags);

The explain_message_fchownat function is used to obtain an explanation of an error returned by the fchownat(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.
dirfd
The original dirfd, exactly as passed to the fchownat(2) system call.
pathname
The original pathname, exactly as passed to the fchownat(2) system call.
owner
The original owner, exactly as passed to the fchownat(2) system call.
group
The original group, exactly as passed to the fchownat(2) system call.
flags
The original flags, exactly as passed to the fchownat(2) system call.

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

if (fchownat(dirfd, pathname, owner, group, flags) < 0)

{
    char message[3000];

explain_message_fchownat(message, sizeof(message), dirfd, pathname, owner, group, flags);

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

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

explain_message_errno_fchownat

void explain_message_errno_fchownat(char *message, int message_size, int errnum, int dirfd, const char *pathname, int owner, int group, int flags);

The explain_message_errno_fchownat function is used to obtain an explanation of an error returned by the fchownat(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.
dirfd
The original dirfd, exactly as passed to the fchownat(2) system call.
pathname
The original pathname, exactly as passed to the fchownat(2) system call.
owner
The original owner, exactly as passed to the fchownat(2) system call.
group
The original group, exactly as passed to the fchownat(2) system call.
flags
The original flags, exactly as passed to the fchownat(2) system call.

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

if (fchownat(dirfd, pathname, owner, group, flags) < 0)

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

explain_message_errno_fchownat(message, sizeof(message), err, dirfd, pathname, owner, group, flags);

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

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

See Also

fchownat(2)
change ownership of a file relative to a directory
explain_fchownat_or_die(3)
change ownership of a file relative to a directory and report errors

Referenced By

explain(3), explain_fchownat_or_die(3).