explain_wait4(3) Library Functions Manual explain_wait4(3) NAME explain_wait4 - explain wait4(2) errors SYNOPSIS #include <libexplain/wait4.h> const char *explain_wait4(int pid, int *status, int options, struct rusage *rusage); const char *explain_errno_wait4(int errnum, int pid, int *status, int op- tions, struct rusage *rusage); void explain_message_wait4(char *message, int message_size, int pid, int *status, int options, struct rusage *rusage); void explain_message_errno_wait4(char *message, int message_size, int er- rnum, int pid, int *status, int options, struct rusage *rusage); DESCRIPTION These functions may be used to obtain explanations for errors returned by the wait4(2) system call. explain_wait4 const char *explain_wait4(int pid, int *status, int options, struct rusage *rusage); The explain_wait4 function is used to obtain an explanation of an error re- turned by the wait4(2) 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: if (wait4(pid, status, options, rusage) < 0) { fprintf(stderr, "%s\n", explain_wait4(pid, status, options, rusage)); exit(EXIT_FAILURE); } pid The original pid, exactly as passed to the wait4(2) system call. status The original status, exactly as passed to the wait4(2) system call. options The original options, exactly as passed to the wait4(2) system call. rusage The original rusage, exactly as passed to the wait4(2) 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_wait4 const char *explain_errno_wait4(int errnum, int pid, int *status, int op- tions, struct rusage *rusage); The explain_errno_wait4 function is used to obtain an explanation of an er- ror returned by the wait4(2) 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: if (wait4(pid, status, options, rusage) < 0) { int err = errno; fprintf(stderr, "%s\n", explain_errno_wait4(err, pid, status, options, rusage)); exit(EXIT_FAILURE); } 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. pid The original pid, exactly as passed to the wait4(2) system call. status The original status, exactly as passed to the wait4(2) system call. options The original options, exactly as passed to the wait4(2) system call. rusage The original rusage, exactly as passed to the wait4(2) 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_wait4 void explain_message_wait4(char *message, int message_size, int pid, int *status, int options, struct rusage *rusage); The explain_message_wait4 function may be used to obtain an explanation of an error returned by the wait4(2) 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: if (wait4(pid, status, options, rusage) < 0) { char message[3000]; explain_message_wait4(message, sizeof(message), pid, status, options, rusage); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } 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. pid The original pid, exactly as passed to the wait4(2) system call. status The original status, exactly as passed to the wait4(2) system call. options The original options, exactly as passed to the wait4(2) system call. rusage The original rusage, exactly as passed to the wait4(2) system call. explain_message_errno_wait4 void explain_message_errno_wait4(char *message, int message_size, int er- rnum, int pid, int *status, int options, struct rusage *rusage); The explain_message_errno_wait4 function may be used to obtain an explana- tion of an error returned by the wait4(2) 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: if (wait4(pid, status, options, rusage) < 0) { int err = errno; char message[3000]; explain_message_errno_wait4(message, sizeof(message), err, pid, status, options, rusage); fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); } 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. pid The original pid, exactly as passed to the wait4(2) system call. status The original status, exactly as passed to the wait4(2) system call. options The original options, exactly as passed to the wait4(2) system call. rusage The original rusage, exactly as passed to the wait4(2) system call. SEE ALSO wait4(2) wait for process to change state explain_wait4_or_die(3) wait for process to change state and report errors COPYRIGHT libexplain version 1.3 Copyright (C) 2008 Peter Miller explain_wait4(3)
NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | COPYRIGHT
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=explain_wait4&sektion=3&manpath=FreeBSD+Ports+15.1.quarterly>