libexplain/popen.h File Reference

explain popen(3) errors More...

#include <libexplain/gcc_attributes.h>
#include <stdio.h>

Go to the source code of this file.

Functions
FILE *	explain_popen_or_die (const char *command, const char *flags)
FILE *	explain_popen_on_error (const char *command, const char *flags) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_popen (const char *command, const char *flags) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_popen (int errnum, const char *command, const char *flags) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_popen (char *message, int message_size, const char *command, const char *flags)
void	explain_message_errno_popen (char *message, int message_size, int errnum, const char *command, const char *flags)

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Detailed Description

explain popen(3) errors

Definition in file popen.h.

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Function Documentation

const char* explain_errno_popen	(	int	errnum,
		const char *	command,
		const char *	flags
	)

The explain_errno_popen function is used to obtain an explanation of an error returned by the popen(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:

 FILE *fp = popen(command, flags);
 if (!fp)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_popen(err, command, flags));
     exit(EXIT_FAILURE);
 }

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

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.
command	The original command, exactly as passed to the popen(3) system call.
flags	The original flags, exactly as passed to the popen(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.

void explain_message_errno_popen	(	char *	message,
		int	message_size,
		int	errnum,
		const char *	command,
		const char *	flags
	)

The explain_message_errno_popen function is used to obtain an explanation of an error returned by the popen(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:

 FILE *fp = popen(command, flags);
 if (!fp)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_popen(message, sizeof(message), err, command,
         flags);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

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.
command	The original command, exactly as passed to the popen(3) system call.
flags	The original flags, exactly as passed to the popen(3) system call.

void explain_message_popen	(	char *	message,
		int	message_size,
		const char *	command,
		const char *	flags
	)

The explain_message_popen function is used to obtain an explanation of an error returned by the popen(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.

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:

 FILE *fp = popen(command, flags);
 if (!fp)
 {
     char message[3000];
     explain_message_popen(message, sizeof(message), command, flags);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

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.
command	The original command, exactly as passed to the popen(3) system call.
flags	The original flags, exactly as passed to the popen(3) system call.

const char* explain_popen	(	const char *	command,
		const char *	flags
	)

The explain_popen function is used to obtain an explanation of an error returned by the popen(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:

 FILE *fp = popen(command, flags);
 if (!fp)
 {
     fprintf(stderr, "%s\n", explain_popen(command, flags));
     exit(EXIT_FAILURE);
 }

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

Parameters:

command	The original command, exactly as passed to the popen(3) system call.
flags	The original flags, exactly as passed to the popen(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.

FILE* explain_popen_on_error	(	const char *	command,
		const char *	flags
	)

The explain_popen_on_error function is used to call the popen(3) system call. On failure an explanation will be printed to stderr, obtained from the explain_popen(3) function.

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

 FILE *fp = explain_popen_on_error(command, flags);
 if (!fp)
 {
     ...cope with error
     ...no need to print error message
 }

Parameters:

command	The command, exactly as to be passed to the popen(3) system call.
flags	The flags, exactly as to be passed to the popen(3) system call.

Returns:

The value returned by the wrapped popen(3) system call.

FILE* explain_popen_or_die	(	const char *	command,
		const char *	flags
	)

The explain_popen_or_die function is used to call the popen(3) system call. On failure an explanation will be printed to stderr, obtained from the explain_popen(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:

 FILE *fp = explain_popen_or_die(command, flags);

Parameters:

command	The command, exactly as to be passed to the popen(3) system call.
flags	The flags, exactly as to be passed to the popen(3) system call.

Returns:

This function only returns on success. On failure, prints an explanation and exits, it does not return.