NAME

       explain_popen - explain popen(3) errors

SYNOPSIS

       #include <libexplain/popen.h>
       const char *explain_popen(const char *command, const char *flags);
       const char *explain_errno_popen(int errnum, const char *command, const char *flags);
       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);

DESCRIPTION

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

   explain_popen
       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(3) function.

       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.

   explain_errno_popen
       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(3) function.

       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.

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

       The  explain_message_popen  function  may  be  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)
              {
                  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(3) function.

       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.

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

       The explain_message_errno_popen function may be 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(3) function.

       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.

SEE ALSO

       popen(3)
               process I/O

       explain_popen_or_die(3)
               process I/O and report errors

COPYRIGHT

       libexplain version 1.4
       Copyright (C) 2009 Peter Miller

                                                                                 explain_popen(3)