libexplain  1.4.D001
Functions
libexplain/chmod.h File Reference

explain chmod(2) errors More...

#include <libexplain/gcc_attributes.h>

Go to the source code of this file.

Functions

void explain_chmod_or_die (const char *pathname, int mode)
int explain_chmod_on_error (const char *pathname, int mode) LIBEXPLAIN_WARN_UNUSED_RESULT
const char * explain_chmod (const char *pathname, int mode) LIBEXPLAIN_WARN_UNUSED_RESULT
const char * explain_errno_chmod (int errnum, const char *pathname, int mode) LIBEXPLAIN_WARN_UNUSED_RESULT
void explain_message_chmod (char *message, int message_size, const char *pathname, int mode)
void explain_message_errno_chmod (char *message, int message_size, int errnum, const char *pathname, int mode)

Detailed Description

explain chmod(2) errors

Definition in file chmod.h.


Function Documentation

const char* explain_chmod ( const char *  pathname,
int  mode 
)

The explain_chmod function is used to obtain an explanation of an error returned by the chmod(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.

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

 if (chmod(pathname, mode) < 0)
 {
     fprintf(stderr, "%s\n", explain_chmod(pathname, mode));
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_chmod_or_die function.

Parameters:
pathnameThe original pathname, exactly as passed to the chmod(2) system call.
modeThe original mode, exactly as passed to the chmod(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.
int explain_chmod_on_error ( const char *  pathname,
int  mode 
)

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

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

 if (explain_chmod_on_error(pathname, mode) < 0)
 {
     ...cope with error
     ...no need to print error message
 }
Parameters:
pathnameThe pathname, exactly as to be passed to the chmod(2) system call.
modeThe mode, exactly as to be passed to the chmod(2) system call.
Returns:
The value returned by the wrapped chmod(2) system call.
void explain_chmod_or_die ( const char *  pathname,
int  mode 
)

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

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

 explain_chmod_or_die(pathname, mode);
Parameters:
pathnameThe pathname, exactly as to be passed to the chmod(2) system call.
modeThe mode, exactly as to be passed to the chmod(2) system call.
Returns:
This function only returns on success. On failure, prints an explanation and exits, it does not return.
const char* explain_errno_chmod ( int  errnum,
const char *  pathname,
int  mode 
)

The explain_errno_chmod function is used to obtain an explanation of an error returned by the chmod(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.

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

 if (chmod(pathname, mode) < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_chmod(err, pathname, mode));
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_chmod_or_die function.

Parameters:
errnumThe 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.
pathnameThe original pathname, exactly as passed to the chmod(2) system call.
modeThe original mode, exactly as passed to the chmod(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.
void explain_message_chmod ( char *  message,
int  message_size,
const char *  pathname,
int  mode 
)

The explain_message_chmod function is used to obtain an explanation of an error returned by the chmod(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.

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

 if (chmod(pathname, mode) < 0)
 {
     char message[3000];
     explain_message_chmod(message, sizeof(message), pathname, mode);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_chmod_or_die function.

Parameters:
messageThe location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.
message_sizeThe size in bytes of the location in which to store the returned message.
pathnameThe original pathname, exactly as passed to the chmod(2) system call.
modeThe original mode, exactly as passed to the chmod(2) system call.
void explain_message_errno_chmod ( char *  message,
int  message_size,
int  errnum,
const char *  pathname,
int  mode 
)

The explain_message_errno_chmod function is used to obtain an explanation of an error returned by the chmod(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.

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

 if (chmod(pathname, mode) < 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_chmod(message, sizeof(message), err, pathname,
         mode);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

The above code example is available pre-packaged as the explain_chmod_or_die function.

Parameters:
messageThe location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.
message_sizeThe size in bytes of the location in which to store the returned message.
errnumThe 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.
pathnameThe original pathname, exactly as passed to the chmod(2) system call.
modeThe original mode, exactly as passed to the chmod(2) system call.