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/*
* libexplain - Explain errno values returned by libc functions
* Copyright (C) 2011, 2013 Peter Miller
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 3 of the License, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
* General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef LIBEXPLAIN_SETSID_H
#define LIBEXPLAIN_SETSID_H
/**
* @file
* @brief explain setsid(2) errors
*
* These functions may be used to obtain explanations for errors returned
* by the <i>setsid</i>(2) system call.
*/
#include <libexplain/gcc_attributes.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* The explain_setsid_or_die function is used to call the <i>setsid</i>(2)
* system call. On failure an explanation will be printed to stderr,
* obtained from the <i>#explain_setsid</i>(3) function, and then the
* process terminates by calling <tt>exit(EXIT_FAILURE)</tt>.
*
* @returns
* This function only returns on success, see <i>setsid</i>(2) for
* more information. On failure, prints an explanation and exits, it
* does not return.
*
* @par Example:
* This function is intended to be used in a fashion similar to the
* following example:
* @code
* explain_setsid_or_die();
* @endcode
*/
pid_t explain_setsid_or_die(void);
/**
* The explain_setsid_on_error function is used to call the
* <i>setsid</i>(2) system call. On failure an explanation will be printed
* to stderr, obtained from the <i>#explain_setsid</i>(3) function.
*
* @returns
* The value returned by the wrapped <i>setsid</i>(2) system call.
*
* @par Example:
* This function is intended to be used in a fashion similar to the
* following example:
* @code
* pid_t result = explain_setsid_on_error();
* if (result < 0)
* {
* ...cope with error
* ...no need to print error message
* }
* @endcode
*/
pid_t explain_setsid_on_error(void);
/**
* The explain_setsid function is used to obtain an explanation of an
* error returned by the <i>setsid</i>(2) system call. The least the
* message will contain is the value of <tt>strerror(errno)</tt>, 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.
*
* @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 <b>not</b> thread safe, because it shares a return
* buffer across all threads, and many other functions in this
* library.
*
* @par Example:
* This function is intended to be used in a fashion similar to the
* following example:
* @code
* pid_t result = setsid();
* if (result < 0)
* {
* fprintf(stderr, "%s\n", explain_setsid());
* exit(EXIT_FAILURE);
* }
* @endcode
* @par
* The above code example is available pre\-packaged as the
* #explain_setsid_or_die function.
*/
const char *explain_setsid(void)
LIBEXPLAIN_WARN_UNUSED_RESULT;
/**
* The explain_errno_setsid function is used to obtain an explanation of
* an error returned by the <i>setsid</i>(2) system call. The least the
* message will contain is the value of <tt>strerror(errnum)</tt>, but
* usually it will do much better, and indicate the underlying cause in
* more detail.
*
* @param 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 <b>any</b> code between the system
* call to be explained and this function, because many libc functions
* will alter the value of errno.
* @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 <b>not</b> thread safe, because it shares a return
* buffer across all threads, and many other functions in this
* library.
*
* @par Example:
* This function is intended to be used in a fashion similar to the
* following example:
* @code
* pid_t result = setsid();
* if (result < 0)
* {
* int err = errno;
* fprintf(stderr, "%s\n", explain_errno_setsid(err, ));
* exit(EXIT_FAILURE);
* }
* @endcode
* @par
* The above code example is available pre-packaged as the
* #explain_setsid_or_die function.
*/
const char *explain_errno_setsid(int errnum)
LIBEXPLAIN_WARN_UNUSED_RESULT;
/**
* The explain_message_setsid function is used to obtain an explanation of
* an error returned by the <i>setsid</i>(2) system call. The least the
* message will contain is the value of <tt>strerror(errnum)</tt>, 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.
*
* @param message
* The location in which to store the returned message. If a suitable
* message return buffer is supplied, this function is thread safe.
* @param message_size
* The size in bytes of the location in which to store the returned
* message.
*
* @par Example:
* This function is intended to be used in a fashion similar to the
* following example:
* @code
* pid_t result = setsid();
* if (result < 0)
* {
* char message[3000];
* explain_message_setsid(message, sizeof(message), );
* fprintf(stderr, "%s\n", message);
* exit(EXIT_FAILURE);
* }
* @endcode
* @par
* The above code example is available pre-packaged as the
* #explain_setsid_or_die function.
*/
void explain_message_setsid(char *message, int message_size);
/**
* The explain_message_errno_setsid function is used to obtain an
* explanation of an error returned by the <i>setsid</i>(2) system call.
* The least the message will contain is the value of
* <tt>strerror(errnum)</tt>, but usually it will do much better, and
* indicate the underlying cause in more detail.
*
* @param message
* The location in which to store the returned message. If a suitable
* message return buffer is supplied, this function is thread safe.
* @param message_size
* The size in bytes of the location in which to store the returned
* message.
* @param 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 <b>any</b> code between the system
* call to be explained and this function, because many libc functions
* will alter the value of errno.
*
* @par Example:
* This function is intended to be used in a fashion similar to the
* following example:
* @code
* pid_t result = setsid();
* if (result < 0)
* {
* int err = errno;
* char message[3000];
* explain_message_errno_setsid(message, sizeof(message), err, );
* fprintf(stderr, "%s\n", message);
* exit(EXIT_FAILURE);
* }
* @endcode
* @par
* The above code example is available pre-packaged as the
* #explain_setsid_or_die function.
*/
void explain_message_errno_setsid(char *message, int message_size, int errnum);
#ifdef __cplusplus
}
#endif
/* vim: set ts=8 sw=4 et : */
#endif /* LIBEXPLAIN_SETSID_H */
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