.\" Copyright (c) 1991 The Regents of the University of California.
.\" %sccs.include.redist.man%
.\" @(#)exec.3 6.3 (Berkeley) %G%
execl, execlp, execle, exect, execv, execvp \- execute a file
execl(const char *path, const char *arg, ...);
execlp(const char *file, const char *arg, ...);
execle(const char *path, const char *arg, ...,
exect(const char *path, char *const argv[],
execv(const char *path, char *const argv[]);
execvp(const char *file, char *const argv[]);
The exec family of functions replaces the current process image with a
The functions described in this manual page are front-ends for the function
for detailed information about the replacement of the current process.)
The initial argument for these functions is the pathname of a file which
The ``const char *arg'' and subsequent ellipses in the
functions can be thought of as
Together they describe a list of one or more pointers to null-terminated
strings that represent the argument list available to the executed program.
The first argument, by convention, should point to the file name associated
with the file being executed.
be terminated by a NULL pointer.
functions provide an array of pointers to null-terminated strings that
represent the argument list available to the new program.
The first argument, by convention, should point to the file name associated
with the file begin executed.
be terminated by a NULL pointer.
functions also specify the environment of the executed process by following
the NULL pointer that terminates the list of arguments in the parameter list
or the pointer to the argv array with an additional parameter.
This additional parameter is an array of pointers to null-terminated strings
be terminated by a NULL pointer.
The other functions take the environment for the new process image from the
Some of these functions have special semantics.
will duplicate the actions of the shell in searching for an executable file
if the specified file name does not contain a slash (``/'') character.
The search path is the path specified in the environment by ``PATH'' variable.
If this variable isn't specified, the default path ``/bin:/usr/bin:'' is
In addtion, certain errors are treated specially.
If permission is denied for a file (the attempted
returned EACCES), these functions will continue searching the rest of
If no other file is found, however, they will return with
If the header of a file isn't recognized (the attempted
returned ENOEXEC), these functions will execute the shell with the path of
the file as its first argument.
(If this attempt fails, no further searching is done.)
If the file is currently busy (the attempted
returned ETXTBUSY), these functions will sleep for several seconds,
periodically re-attempting to execute the file.
executes a file with the program tracing facilities enabled (see
functions returns, an error will have occurred.
The return value is -1, and
will be set to indicate the error.
for any of the errors specified for the library functions
for any of the errors specified for the library function
sh(1), execve(2), fork(2), ptrace(2), environ(7),
Historically, the default path for the
functions was ``:/bin:/usr/bin''.
This was changed to place the current directory last to enhance system
when errors occur while attempting to execute the file is historic
practice, but has not traditionally been documented and is not specified
Traditionally, the functions
ignored all errors except for the ones described above and ENOMEM and
E2BIG, upon which they returned.
They now return if any error other than the ones described above occurs.
conform to IEEE Std 1003.1-1988 (``POSIX'').