EXEC

Section: MINTLIB LIBRARY FUNCTIONS (3)
Updated: 3 March 1993
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NAME

execl, execv, execle, execlp, execve, execvp - execute a file

SYNOPSIS

#include <unistd.h>

int execl(char *path, ...);

int execv(char *path, char *argv[]);

int execle(char *path, ...);

int execlp(char *file, ...);

int execve(char *path, char *argv[], char *envp[]);

int execvp(char *file, char *argv[]);

DESCRIPTION

These routines transform the calling process into a new process. The program indicated by `path' or `file' is loaded, then run. There can be no return from a succesful exec call. These calls differ in the following ways:
- execl, execle and execlp are called when the number of
  arguments is known in advance, whereas execv, execve
  and execvp take an argument vector. - execl, execv, execle and execve are called with the full
  path name of the program to be run, whereas execlp and
  execvp are called with a filename that is searched on
  the user's search path and that may be extended with
  the filename extensions ".ttp", ".tos" and ".prg". - execl, execv, execlp and execvp pass the parent's
  environment to the new process, whereas execle and
  execve take a pointer to an environment vector as
  their final argument. The last argument to the execl, execle and execlp functions should be a NULL pointer. An argument vector argv as used in execv, execve and execvp is a pointer to a null-terminated array of character pointers to null-terminated character strings. These strings constitute the argument list to be made available to the new process. By convention, at least one argument must be present in this array, and the first element of this array should be the name of the executed program. For execv and execve this is the last component of the path argument; for execvp this is the file argument. The environment vector envp as used in execle and execve is also a pointer to a null-terminated array of character pointers to null-terminated strings. These strings pass information to the new process which are not directly arguments to the command. If envp is NULL, a copy of the parent process' environment is passed. Signals set to the default action (SIG_DFL) in the calling process image are set to the default action in the new process. Signals set to be ignored (SIG_IGN) by the calling process are ignored by the new process. Signals set to be caught by the calling process are reset to the default action in the new process. Signals set to be blocked in the calling process remain blocked in the new process, regardless of changes to the signal action.

RETURN VALUES

These functions returns to the calling process only on failure, for instance if the program called could not be found, if it was not executable, or if not enough memory was available, in which case -1 is returned and errno is set to indicate the error.

EXAMPLES

  This will execute the program /bin/date or fail:
execl("/bin/date", "date", NULL);

  This will search the program sh and then execute it;
  it will fail only if sh, sh.tos, sh.ttp and sh.prg
  could not be found:
execlp("sh", "sh", "-c", commandline, NULL);

  This will call /bin/test using an already constructed
  argument vector and an already constructed environment
  vector, and fail if /bin/test could not be found:
execve("/bin/test", my_argv, my_envp);

NOTES

When MiNT is not active, these library calls call a child process and then _exit after the child has finished; only when MiNT is active, the current process is truly transformed into a new one. On Un*x, execve is a system call, while the rest of these calls are library routines. Under MiNT, it's all done in the library.

This document was created by man2html, using the manual pages.
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