libexplain/unsetenv.h File Reference

explain unsetenv(3) errors More...

#include <libexplain/gcc_attributes.h>

Go to the source code of this file.

Functions
void	explain_unsetenv_or_die (const char *name)
int	explain_unsetenv_on_error (const char *name)
const char *	explain_unsetenv (const char *name) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_unsetenv (int errnum, const char *name) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_unsetenv (char *message, int message_size, const char *name)
void	explain_message_errno_unsetenv (char *message, int message_size, int errnum, const char *name)

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Detailed Description

explain unsetenv(3) errors

These functions may be used to obtain explanations for errors returned by the unsetenv(3) system call.

Definition in file unsetenv.h.

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Function Documentation

const char* explain_errno_unsetenv	(	int	errnum,
		const char *	name
	)

The explain_errno_unsetenv function is used to obtain an explanation of an error returned by the unsetenv(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.

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.
name	The original name, exactly as passed to the unsetenv(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.

Example:

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

 if (unsetenv(name) < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_unsetenv(err, name));
     exit(EXIT_FAILURE);
 }

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

void explain_message_errno_unsetenv	(	char *	message,
		int	message_size,
		int	errnum,
		const char *	name
	)

The explain_message_errno_unsetenv function is used to obtain an explanation of an error returned by the unsetenv(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.

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.
name	The original name, exactly as passed to the unsetenv(3) system call.

Example:

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

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

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

void explain_message_unsetenv	(	char *	message,
		int	message_size,
		const char *	name
	)

The explain_message_unsetenv function is used to obtain an explanation of an error returned by the unsetenv(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.

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.
name	The original name, exactly as passed to the unsetenv(3) system call.

Example:

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

 if (unsetenv(name) < 0)
 {
     char message[3000];
     explain_message_unsetenv(message, sizeof(message), name);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

const char* explain_unsetenv

(

const char *

name

)

The explain_unsetenv function is used to obtain an explanation of an error returned by the unsetenv(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.

Parameters:

name	The original name, exactly as passed to the unsetenv(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.

Example:

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

 if (unsetenv(name) < 0)
 {
     fprintf(stderr, "%s\n", explain_unsetenv(name));
     exit(EXIT_FAILURE);
 }

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

int explain_unsetenv_on_error

(

const char *

name

)

The explain_unsetenv_on_error function is used to call the unsetenv(3) system call. On failure an explanation will be printed to stderr, obtained from the explain_unsetenv(3) function.

Parameters:

name	The name, exactly as to be passed to the unsetenv(3) system call.

Returns:

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

Example:

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

 if (explain_unsetenv_on_error(name) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

void explain_unsetenv_or_die

(

const char *

name

)

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

Parameters:

name	The name, exactly as to be passed to the unsetenv(3) system call.

Returns:

This function only returns on success, see unsetenv(3) for more information. On failure, prints an explanation and exits, it does not return.

Example:

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

 explain_unsetenv_or_die(name);