explain_popen(3) Library Functions Manual explain_popen(3) 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 er- rnum, 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 re- turned 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 indi- cate the underlying cause in more detail. The errno global variable will be used to obtain the error value to be de- coded. 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 ex- plain_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 ar- gument list. This will be overwritten by the next call to any lib- explain 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 er- ror returned by the popen(3) system call. The least the message will con- tain 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 ex- plain_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 nec- essary 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 ar- gument list. This will be overwritten by the next call to any lib- explain 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 bet- ter, and indicate the underlying cause in more detail. The errno global variable will be used to obtain the error value to be de- coded. 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 ex- plain_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 er- rnum, const char *command, const char *flags); The explain_message_errno_popen function may be used to obtain an explana- tion of an error returned by the popen(3) system call. The least the mes- sage 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 ex- plain_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 nec- essary 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 1.3 Copyright (C) 2009 Peter Miller explain_popen(3)
NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT
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