Linux Error Return Execvp
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char *pathname, char *const *argv); void explain_message_execvp(char *message, int message_size, const char *pathname, char *const *argv); void explain_message_errno_execvp(char *message, int message_size, int errnum, const char *pathname, char *const *argv); Description These functions may be used to obtain explanations for errors returned execvp example by the execvp(3) system call. explain_execvp const char *explain_execvp(const char *pathname, char *const
What Does Execvp Return
*argv); The explain_execvp function is used to obtain an explanation of an error returned by the execvp(3) system call. The
Execvp C
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
Execvp Man
obtain the error value to be decoded. This function is intended to be used in a fashion similar to the following example: if (execvp(pathname, argv) < 0) { fprintf(stderr, "%s\n", explain_execvp(pathname, argv)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_execvp_or_die(3) function. pathname The original pathname, exactly as passed to the execvp(3) system call. argv The original argv, exactly as passed to the execvp(3) execvp arguments 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_execvp const char *explain_errno_execvp(int errnum, const char *pathname, char *const *argv); The explain_errno_execvp function is used to obtain an explanation of an error returned by the execvp(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: if (execvp(pathname, argv) < 0) { int err = errno; fprintf(stderr, "%s\n", explain_errno_execvp(err, pathname, argv)); exit(EXIT_FAILURE); } The above code example is available pre-packaged as the explain_execvp_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 cod
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn execvp c++ more about Stack Overflow the company Business Learn more about hiring developers or execvp syntax posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community what does execvp do Stack Overflow is a community of 6.2 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up Handling errors from execvp() up vote 2 down vote https://linux.die.net/man/3/explain_execvp favorite 1 I am a little confused about how to handle errors from execvp(). My code so far looks like this: int pid = fork(); if (pid < 0) { // handle error. } else if (pid == 0) { int status = execvp(myCommand,myArgumentVector); // status should be -1 because execvp // only returns when an error occurs // We only reach this point as a result of http://stackoverflow.com/questions/20063803/handling-errors-from-execvp failure from execvp exit(/* What goes here? */); } else { int status; int waitedForPid = waitpid(pid,&status,0); //... } There are three cases I'm trying to address: myCommand,myArgumentVector are valid and the command executes correctly. myCommand,myArgumentVector are valid parameters, but something goes wrong in the execution of myCommand. myCommand,myArgumentVector are invalid parameters (e.g. myCommand cannot be found) and the execvp() call fails. My primary concern is that the parent process will have all the information it needs in order to handle the child's error correctly, and I'm not entirely sure how to do that. In the first case, the program presumably ended with an exit status of 0. This means that if I were to call WIFEXITED(status) in the macro, I should get true. I think this should work fine. In the second case, the program presumably ended with an exit status other than 0. This means that if I were to call WEXITSTATUS(status) I should get the specific exit status of the child invocation of myCommand (please advise if this is incorrect). The third case is causing me a lot of confusion. So if execvp() fails then the error is stored in the global variable errno. But this global variable
execvp(const char *path, char *const argv[]); DESCRIPTION
Like all of the exec functions, execvp replaces the calling process image with a new process image. This has the effect of running a new https://support.sas.com/documentation/onlinedoc/sasc/doc700/html/lr2/zid-7307.htm program with the process ID of the calling process. Note that a new process is not started; the new process image simply overlays the original process image. The execvp function is most commonly used to overlay a process image that has been created by a call to the fork function.
path
identifies the location of the new process what does image within the hierarchical file system (HFS). If the path argument contains a slash ( / ), it is assumed that either an absolute or a relative pathname has been specified. If the path argument does not contain a slash, the directories specified by the PATH environment variable are searched in an attempt to locate the file.
argv
is a pointer to an array of pointers to null-terminated character strings. A NULL pointer is used to mark the end of the array. Each character string pointed to by the array is used to pass an argument to the new process image. The first argument, argv[0] , is required and must contain the name of the executable file for the new process image. RETURN VALUE
A successful call to execvp does not have a return value because the new process image overlays the calling process image. However, a -1 is returned if the call to execvp is unsuccessful. EXAMPLE
The following example illustrates the use of execvp to execute the ls shell command: #include