NAME
explain_system - explain system(3) errors
SYNOPSIS
#include <libexplain/system.h>
const char *explain_system(const char *command);
const char *explain_errno_system(int errnum, const char *command);
void explain_message_system(char *message, int message_size, const char
*command);
void explain_message_errno_system(char *message, int message_size, int
errnum, const char *command);
DESCRIPTION
These functions may be used to obtain explanations for errors returned
by the system(3) system call.
explain_system
const char *explain_system(const char *command);
The explain_system function is used to obtain an explanation of an
error returned by the system(3) 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 (system(command) < 0)
{
fprintf(stderr, "%s\n", explain_system(command));
exit(EXIT_FAILURE);
}
command The original command, exactly as passed to the system(3) 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.
explain_errno_system
const char *explain_errno_system(int errnum, const char *command);
The explain_errno_system function is used to obtain an explanation of
an error returned by the system(3) 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 (system(command) < 0)
{
int err = errno;
fprintf(stderr, "%s\n", explain_errno_system(err, command));
exit(EXIT_FAILURE);
}
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.
command The original command, exactly as passed to the system(3) 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.
explain_message_system
void explain_message_system(char *message, int message_size, const char
*command);
The explain_message_system function may be used to obtain an
explanation of an error returned by the system(3) 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 (system(command) < 0)
{
char message[3000];
explain_message_system(message, sizeof(message), command);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
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.
command The original command, exactly as passed to the system(3) system
call.
explain_message_errno_system
void explain_message_errno_system(char *message, int message_size, int
errnum, const char *command);
The explain_message_errno_system function may be used to obtain an
explanation of an error returned by the system(3) 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 (system(command) < 0)
{
int err = errno;
char message[3000];
explain_message_errno_system(message, sizeof(message), err, command);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
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.
command The original command, exactly as passed to the system(3) system
call.
SEE ALSO
system(3)
execute a shell command
explain_system_or_die(3)
execute a shell command and report errors
COPYRIGHT
libexplain version 0.19
Copyright (C) 2008 Peter Miller
explain_system(3)