execl.html

unix 下的C开发手册,还用详细的例程。

with the new process image.
<p>
If the Message Passing option is supported, all open message queue 
descriptors in the calling process are closed, as described in
<i><a href="mq_close.html">mq_close()</a></i>.
<p>
If the Asynchronous Input and Output option is supported,
any outstanding asynchronous I/O operations may be canceled.
Those asynchronous I/O operations that are not canceled will complete
as if the
<i>exec</i>
function had not yet occurred,
but any associated signal notifications are suppressed.
It is unspecified whether the
<i>exec</i>
function itself blocks awaiting such I/O completion.
In no event, however, will the new process image created by the
<i>exec</i>
function be affected by the presence of outstanding asynchronous I/O
operations
at the time the
<i>exec</i>
function is called.
Whether any I/O is cancelled, and which I/O may be cancelled upon
<i>exec</i>,
is implementation-dependent.
<p>
The new process also inherits at least the following
attributes from the calling process image:
<p>
nice value (see
<i><a href="nice.html">nice()</a></i>)
<br>
<i>semadj</i> values (see
<i><a href="semop.html">semop()</a></i>)
<br>
process ID
<br>
parent process ID
<br>
process group ID
<br>
session membership
<br>
real user ID
<br>
real group ID
<br>
supplementary group IDs
<br>
time left until an alarm clock signal (see
<i><a href="alarm.html">alarm()</a></i>)
<br>
current working directory
<br>
root directory
<br>
file mode creation mask (see
<i><a href="umask.html">umask()</a></i>)
<br>
file size limit (see
<i><a href="ulimit.html">ulimit()</a></i>)
<br>
process signal mask (see
<i><a href="sigprocmask.html">sigprocmask()</a></i>)
<br>
pending signal (see
<i><a href="sigpending.html">sigpending()</a></i>)
<br>
<i>tms_utime</i>,
<i>tms_stime</i>,
<i>tms_cutime</i>,
and
<i>tms_cstime</i>
(see
<i><a href="times.html">times()</a></i>)
<br>
resource limits
<br>
controlling terminal
<br>
interval timers
<p>
All other process attributes defined in this document will be the same
in the new and old process images.
The inheritance of process attributes not defined by this specification
is implementation-dependent.
<p>
A call to any
<i>exec</i>
function from a process with more than one thread results
in all threads being terminated
and the new executable image being loaded and executed.
No destructor functions will be called.
<p>
Upon successful completion, the
<i>exec</i>
functions mark for update the
<i>st_atime</i>
field of the file. If an
<i>exec</i>
function failed but was able to locate the
<i>process image file</i>,
whether the
<i>st_atime</i>
field is marked for update is unspecified. Should the
<i>exec</i>
function succeed, the process image file is considered to have been opened
with
<i><a href="open.html">open()</a></i>.
The corresponding
<i><a href="close.html">close()</a></i>
is considered to occur at a time after this open, but before
process termination or successful completion of a subsequent call to
one of the
<i>exec</i>
functions.
The argv[] and envp[]
arrays of pointers and the strings to which those
arrays point will not be modified by a call to one of the
<i>exec</i>
functions, except as a consequence of replacing the process image.
<p>
The saved resource limits in the new process image are set to be a copy
of the process's corresponding hard and soft limits.
</blockquote><h4><a name = "tag_000_004_059">&nbsp;</a>RETURN VALUE</h4><blockquote>
If one of the
<i>exec</i>
functions returns to the calling process image, an error has occurred;
the return value is -1, and
<i>errno</i>
is set to indicate the error.
<br>
</blockquote><h4><a name = "tag_000_004_060">&nbsp;</a>ERRORS</h4><blockquote>
The
<i>exec</i>
functions
will fail
if:
<dl compact>

<dt>[E2BIG]<dd>
The number of bytes used by the new process image's
argument list and environment list is greater than the system-imposed
limit of {ARG_MAX} bytes.


<dt>[EACCES]<dd>
Search permission is denied for a directory listed in the new
process image file's path prefix, or the new process image file
denies execution permission, or the new process image file
is not a regular file and the implementation does not support
execution of files of its type.

<dt>[ELOOP]<dd>
Too many symbolic links were encountered in resolving <i>path</i>.

<dt>[ENAMETOOLONG]<dd>

The length of the
<i>path</i>
or
<i>file</i>
arguments, or an element of the environment variable
prefixed to a file, exceeds {PATH_MAX}, or a pathname component
is longer than {NAME_MAX}.

<dt>[ENOENT]<dd>
A component of <i>path</i> or <i>file</i> does not name an existing file
or <i>path</i> or <i>file</i> is an empty string.

<dt>[ENOTDIR]<dd>
A component of the new process image file's path prefix is
not a directory.

</dl>
<p>
The
<i>exec</i>
functions, except for
<i><a href="exec.html">execlp()</a></i>
and
<i><a href="exec.html">execvp()</a></i>,
will fail if:
<dl compact>

<dt>[ENOEXEC]<dd>
The new process image file has the appropriate access permission but
is not in the proper format.

</dl>
<p>
The
<i>exec</i>
functions
may fail if:
<dl compact>

<dt>[ENAMETOOLONG]<dd>

Pathname resolution of a symbolic link produced an intermediate result whose
length exceeds {PATH_MAX}.

<dt>[ENOMEM]<dd>
The new process image requires more memory than is allowed by
the hardware or system-imposed memory management constraints.

<dt>[ETXTBSY]<dd>
The new process image
file is a pure procedure (shared text) file that is
currently open for writing by some process.

</dl>
</blockquote><h4><a name = "tag_000_004_061">&nbsp;</a>EXAMPLES</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_004_062">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
As the state of conversion descriptors and message catalogue
descriptors in the new process image is undefined, portable
applications should not rely on their use and should close
them prior to calling one of the
<i>exec</i>
functions.
<p>
Applications that require other than the default POSIX locale
should call
<i><a href="setlocale.html">setlocale()</a></i>
with the appropriate parameters to establish the locale of the
new process.
<p>
The
<i>environ</i>
array should not be accessed directly by the application.
</blockquote><h4><a name = "tag_000_004_063">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_004_064">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="alarm.html">alarm()</a></i>,
<i><a href="atexit.html">atexit()</a></i>,
<i><a href="chmod.html">chmod()</a></i>,
<i><a href="exit.html">exit()</a></i>,
<i><a href="fcntl.html">fcntl()</a></i>,
<i><a href="fork.html">fork()</a></i>,
<i><a href="fstatvfs.html">fstatvfs()</a></i>,
<i><a href="getenv.html">getenv()</a></i>,
<i><a href="getitimer.html">getitimer()</a></i>,
<i><a href="getrlimit.html">getrlimit()</a></i>,
<i><a href="mmap.html">mmap()</a></i>,
<i><a href="nice.html">nice()</a></i>,
<i><a href="putenv.html">putenv()</a></i>,
<i><a href="semop.html">semop()</a></i>,
<i><a href="setlocale.html">setlocale()</a></i>,
<i><a href="shmat.html">shmat()</a></i>,
<i><a href="sigaction.html">sigaction()</a></i>,
<i><a href="sigaltstack.html">sigaltstack()</a></i>,
<i><a href="sigpending.html">sigpending()</a></i>,
<i><a href="sigprocmask.html">sigprocmask()</a></i>,
<i><a href="system.html">system()</a></i>,
<i><a href="times.html">times()</a></i>,
<i><a href="ulimit.html">ulimit()</a></i>,
<i><a href="umask.html">umask()</a></i>,
<i><a href="unistd.h.html">&lt;unistd.h&gt;</a></i>,
<b>XBD</b> specification, <a href="../xbd/termios.html"><b>General Terminal Interface</b>&nbsp;</a>.
<br>
</blockquote><h4>DERIVATION</h4><blockquote>
Derived from Issue 1 of the SVID.
</blockquote><hr size=2 noshade>
<center><font size=2>
UNIX &reg; is a registered Trademark of The Open Group.<br>
Copyright &copy; 1997 The Open Group
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