int
execl(
const char *path
, const char *arg
, ...
)
int
execlp(
const char *file
, const char *arg
, ...
)
int
execle(
const char *path
, const char *arg
, ...
, char *const envp[]
)
int
exect(
const char *path
, char *const argv[]
, char *const envp[]
)
int
execv(
const char *path
, char *const argv[]
)
int
execvp(
const char *file
, char *const argv[]
)
The initial argument for these functions is the pathname of a file which is to be executed.
The
const char *arg
and subsequent ellipses in the
execl(),
execlp(
),
and
execle(
)
functions can be thought of as
arg0,
arg1,
...,
argn.
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.
The list of arguments
must
be terminated by a
NULL
pointer.
The
exect(),
execv(
),
and
execvp(
)
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 being executed.
The array of pointers
must
be terminated by a
NULL
pointer.
The
execle()
and
exect(
)
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
and
must
be terminated by a
NULL
pointer.
The other functions take the environment for the new process image from the
external variable
environ
in the current process.
Some of these functions have special semantics.
The functions
execlp()
and
execvp(
)
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 the
PATH
variable.
If this variable isn't specified,
_PATH_DEFPATH
from
<paths.h
>
is used instead, its value being:
/usr/bin:/bin:/usr/pkg/bin:/usr/local/bin
.
In addition, certain errors are treated specially.
If permission is denied for a file (the attempted
execve(2)
returned
EACCES
),
these functions will continue searching the rest of
the search path.
If no other file is found, however, they will return with the global variable
errno
set to
EACCES
.
If the header of a file isn't recognized (the attempted
execve(2)
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
execve(2)
returned
ETXTBUSY
),
these functions will sleep for several seconds,
periodically re-attempting to execute the file.
The function
exect()
executes a file with the program tracing facilities enabled (see
ptrace(2)).
/bin/sh
),
execle(
),
execlp(
)
and
execvp(
)
may fail and set
errno
for any of the errors specified for the library functions
execve(2)
and
malloc(3).
exect()
and
execv(
)
may fail and set
errno
for any of the errors specified for the library function
execve(2).
)
and
execvp(
)
functions was
``
:/bin:/usr/bin
''.
This was changed to improve security and behaviour.
The behavior of
execlp()
and
execvp(
)
when errors occur while attempting to execute the file is historic
practice, but has not traditionally been documented and is not specified
by the
POSIX
standard.
Traditionally, the functions
execlp()
and
execvp(
)
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.
),
execv(
),
execle(
),
execlp(
)
and
execvp(
)
conform to
ISO/IEC 9945-1:1990 (``POSIX.1'') .