315 lines
15 KiB
HTML
315 lines
15 KiB
HTML
|
<HTML><HEAD><TITLE>Tcl Built-In Commands - exec manual page</TITLE></HEAD><BODY>
|
||
|
|
<DL>
|
||
|
|
<DD><A HREF="exec.htm#M2" NAME="L206">NAME</A>
|
||
|
|
<DL><DD>exec - Invoke subprocess(es)</DL>
|
||
|
|
<DD><A HREF="exec.htm#M3" NAME="L207">SYNOPSIS</A>
|
||
|
|
<DL>
|
||
|
|
<DD><B>exec </B>?<I>switches</I>? <I>arg </I>?<I>arg ...</I>?
|
||
|
|
</DL>
|
||
|
|
<DD><A HREF="exec.htm#M4" NAME="L208">DESCRIPTION</A>
|
||
|
|
<DL>
|
||
|
|
<DD><A HREF="exec.htm#M5" NAME="L209"><B>-keepnewline</B></A>
|
||
|
|
<DD><A HREF="exec.htm#M6" NAME="L210"><B>- -</B></A>
|
||
|
|
</DL>
|
||
|
|
<DL>
|
||
|
|
<DD><A HREF="exec.htm#M7" NAME="L211">|</A>
|
||
|
|
<DD><A HREF="exec.htm#M8" NAME="L212">|&</A>
|
||
|
|
<DD><A HREF="exec.htm#M9" NAME="L213">< <I>fileName</I></A>
|
||
|
|
<DD><A HREF="exec.htm#M10" NAME="L214"><@ <I>fileId</I></A>
|
||
|
|
<DD><A HREF="exec.htm#M11" NAME="L215"><< <I>value</I></A>
|
||
|
|
<DD><A HREF="exec.htm#M12" NAME="L216">> <I>fileName</I></A>
|
||
|
|
<DD><A HREF="exec.htm#M13" NAME="L217">2> <I>fileName</I></A>
|
||
|
|
<DD><A HREF="exec.htm#M14" NAME="L218">>& <I>fileName</I></A>
|
||
|
|
<DD><A HREF="exec.htm#M15" NAME="L219">>> <I>fileName</I></A>
|
||
|
|
<DD><A HREF="exec.htm#M16" NAME="L220">2>> <I>fileName</I></A>
|
||
|
|
<DD><A HREF="exec.htm#M17" NAME="L221">>>& <I>fileName</I></A>
|
||
|
|
<DD><A HREF="exec.htm#M18" NAME="L222">>@ <I>fileId</I></A>
|
||
|
|
<DD><A HREF="exec.htm#M19" NAME="L223">2>@ <I>fileId</I></A>
|
||
|
|
<DD><A HREF="exec.htm#M20" NAME="L224">>&@ <I>fileId</I></A>
|
||
|
|
</DL>
|
||
|
|
<DD><A HREF="exec.htm#M21" NAME="L225">PORTABILITY ISSUES</A>
|
||
|
|
<DL>
|
||
|
|
<DD><A HREF="exec.htm#M22" NAME="L226"><B>Windows</B> (all versions)</A>
|
||
|
|
<DD><A HREF="exec.htm#M23" NAME="L227"><B>Windows NT</B></A>
|
||
|
|
<DD><A HREF="exec.htm#M24" NAME="L228"><B>Windows 95</B></A>
|
||
|
|
<DD><A HREF="exec.htm#M25" NAME="L229"><B>Macintosh</B></A>
|
||
|
|
<DD><A HREF="exec.htm#M26" NAME="L230"><B>Unix</B></A>
|
||
|
|
</DL>
|
||
|
|
<DD><A HREF="exec.htm#M27" NAME="L231">SEE ALSO</A>
|
||
|
|
<DD><A HREF="exec.htm#M28" NAME="L232">KEYWORDS</A>
|
||
|
|
</DL><HR>
|
||
|
|
<H3><A NAME="M2">NAME</A></H3>
|
||
|
|
exec - Invoke subprocess(es)
|
||
|
|
<H3><A NAME="M3">SYNOPSIS</A></H3>
|
||
|
|
<B>exec </B>?<I>switches</I>? <I>arg </I>?<I>arg ...</I>?<BR>
|
||
|
|
<H3><A NAME="M4">DESCRIPTION</A></H3>
|
||
|
|
This command treats its arguments as the specification
|
||
|
|
of one or more subprocesses to execute.
|
||
|
|
The arguments take the form of a standard shell pipeline
|
||
|
|
where each <I>arg</I> becomes one word of a command, and
|
||
|
|
each distinct command becomes a subprocess.
|
||
|
|
<P>
|
||
|
|
If the initial arguments to <B>exec</B> start with <B>-</B> then
|
||
|
|
they are treated as command-line switches and are not part
|
||
|
|
of the pipeline specification. The following switches are
|
||
|
|
currently supported:
|
||
|
|
<P>
|
||
|
|
<DL>
|
||
|
|
<P><DT><A NAME="M5"><B>-keepnewline</B></A><DD>
|
||
|
|
Retains a trailing newline in the pipeline's output.
|
||
|
|
Normally a trailing newline will be deleted.
|
||
|
|
<P><DT><A NAME="M6"><B>- -</B></A><DD>
|
||
|
|
Marks the end of switches. The argument following this one will
|
||
|
|
be treated as the first <I>arg</I> even if it starts with a <B>-</B>.
|
||
|
|
<P></DL>
|
||
|
|
<P>
|
||
|
|
If an <I>arg</I> (or pair of <I>arg</I>'s) has one of the forms
|
||
|
|
described below then it is used by <B>exec</B> to control the
|
||
|
|
flow of input and output among the subprocess(es).
|
||
|
|
Such arguments will not be passed to the subprocess(es). In forms
|
||
|
|
such as ``< <I>fileName</I>'' <I>fileName</I> may either be in a
|
||
|
|
separate argument from ``<'' or in the same argument with no
|
||
|
|
intervening space (i.e. ``<<I>fileName</I>'').
|
||
|
|
<P>
|
||
|
|
<DL>
|
||
|
|
<P><DT><A NAME="M7">|</A><DD>
|
||
|
|
Separates distinct commands in the pipeline. The standard output
|
||
|
|
of the preceding command will be piped into the standard input
|
||
|
|
of the next command.
|
||
|
|
<P><DT><A NAME="M8">|&</A><DD>
|
||
|
|
Separates distinct commands in the pipeline. Both standard output
|
||
|
|
and standard error of the preceding command will be piped into
|
||
|
|
the standard input of the next command.
|
||
|
|
This form of redirection overrides forms such as 2> and >&.
|
||
|
|
<P><DT><A NAME="M9">< <I>fileName</I></A><DD>
|
||
|
|
The file named by <I>fileName</I> is opened and used as the standard
|
||
|
|
input for the first command in the pipeline.
|
||
|
|
<P><DT><A NAME="M10"><@ <I>fileId</I></A><DD>
|
||
|
|
<I>FileId</I> must be the identifier for an open file, such as the return
|
||
|
|
value from a previous call to <B><A HREF="../TkCmd/open.htm">open</A></B>.
|
||
|
|
It is used as the standard input for the first command in the pipeline.
|
||
|
|
<I>FileId</I> must have been opened for reading.
|
||
|
|
<P><DT><A NAME="M11"><< <I>value</I></A><DD>
|
||
|
|
<I>Value</I> is passed to the first command as its standard input.
|
||
|
|
<P><DT><A NAME="M12">> <I>fileName</I></A><DD>
|
||
|
|
Standard output from the last command is redirected to the file named
|
||
|
|
<I>fileName</I>, overwriting its previous contents.
|
||
|
|
<P><DT><A NAME="M13">2> <I>fileName</I></A><DD>
|
||
|
|
Standard error from all commands in the pipeline is redirected to the
|
||
|
|
file named <I>fileName</I>, overwriting its previous contents.
|
||
|
|
<P><DT><A NAME="M14">>& <I>fileName</I></A><DD>
|
||
|
|
Both standard output from the last command and standard error from all
|
||
|
|
commands are redirected to the file named <I>fileName</I>, overwriting
|
||
|
|
its previous contents.
|
||
|
|
<P><DT><A NAME="M15">>> <I>fileName</I></A><DD>
|
||
|
|
Standard output from the last command is
|
||
|
|
redirected to the file named <I>fileName</I>, appending to it rather
|
||
|
|
than overwriting it.
|
||
|
|
<P><DT><A NAME="M16">2>> <I>fileName</I></A><DD>
|
||
|
|
Standard error from all commands in the pipeline is
|
||
|
|
redirected to the file named <I>fileName</I>, appending to it rather
|
||
|
|
than overwriting it.
|
||
|
|
<P><DT><A NAME="M17">>>& <I>fileName</I></A><DD>
|
||
|
|
Both standard output from the last command and standard error from
|
||
|
|
all commands are redirected to the file named <I>fileName</I>,
|
||
|
|
appending to it rather than overwriting it.
|
||
|
|
<P><DT><A NAME="M18">>@ <I>fileId</I></A><DD>
|
||
|
|
<I>FileId</I> must be the identifier for an open file, such as the return
|
||
|
|
value from a previous call to <B><A HREF="../TkCmd/open.htm">open</A></B>.
|
||
|
|
Standard output from the last command is redirected to <I>fileId</I>'s
|
||
|
|
file, which must have been opened for writing.
|
||
|
|
<P><DT><A NAME="M19">2>@ <I>fileId</I></A><DD>
|
||
|
|
<I>FileId</I> must be the identifier for an open file, such as the return
|
||
|
|
value from a previous call to <B><A HREF="../TkCmd/open.htm">open</A></B>.
|
||
|
|
Standard error from all commands in the pipeline is
|
||
|
|
redirected to <I>fileId</I>'s file.
|
||
|
|
The file must have been opened for writing.
|
||
|
|
<P><DT><A NAME="M20">>&@ <I>fileId</I></A><DD>
|
||
|
|
<I>FileId</I> must be the identifier for an open file, such as the return
|
||
|
|
value from a previous call to <B><A HREF="../TkCmd/open.htm">open</A></B>.
|
||
|
|
Both standard output from the last command and standard error from
|
||
|
|
all commands are redirected to <I>fileId</I>'s file.
|
||
|
|
The file must have been opened for writing.
|
||
|
|
<P></DL>
|
||
|
|
<P>
|
||
|
|
If standard output has not been redirected then the <B>exec</B>
|
||
|
|
command returns the standard output from the last command
|
||
|
|
in the pipeline.
|
||
|
|
If any of the commands in the pipeline exit abnormally or
|
||
|
|
are killed or suspended, then <B>exec</B> will return an error
|
||
|
|
and the error message will include the pipeline's output followed by
|
||
|
|
error messages describing the abnormal terminations; the
|
||
|
|
<B>errorCode</B> variable will contain additional information
|
||
|
|
about the last abnormal termination encountered.
|
||
|
|
If any of the commands writes to its standard error file and that
|
||
|
|
standard error isn't redirected,
|
||
|
|
then <B>exec</B> will return an error; the error message
|
||
|
|
will include the pipeline's standard output, followed by messages
|
||
|
|
about abnormal terminations (if any), followed by the standard error
|
||
|
|
output.
|
||
|
|
<P>
|
||
|
|
If the last character of the result or error message
|
||
|
|
is a newline then that character is normally deleted
|
||
|
|
from the result or error message.
|
||
|
|
This is consistent with other Tcl return values, which don't
|
||
|
|
normally end with newlines.
|
||
|
|
However, if <B>-keepnewline</B> is specified then the trailing
|
||
|
|
newline is retained.
|
||
|
|
<P>
|
||
|
|
If standard input isn't redirected with ``<'' or ``<<''
|
||
|
|
or ``<@'' then the standard input for the first command in the
|
||
|
|
pipeline is taken from the application's current standard input.
|
||
|
|
<P>
|
||
|
|
If the last <I>arg</I> is ``&'' then the pipeline will be
|
||
|
|
executed in background.
|
||
|
|
In this case the <B>exec</B> command will return a list whose
|
||
|
|
elements are the process identifiers for all of the subprocesses
|
||
|
|
in the pipeline.
|
||
|
|
The standard output from the last command in the pipeline will
|
||
|
|
go to the application's standard output if it hasn't been
|
||
|
|
redirected, and error output from all of
|
||
|
|
the commands in the pipeline will go to the application's
|
||
|
|
standard error file unless redirected.
|
||
|
|
<P>
|
||
|
|
The first word in each command is taken as the command name;
|
||
|
|
tilde-substitution is performed on it, and if the result contains
|
||
|
|
no slashes then the directories
|
||
|
|
in the PATH environment variable are searched for
|
||
|
|
an executable by the given name.
|
||
|
|
If the name contains a slash then it must refer to an executable
|
||
|
|
reachable from the current directory.
|
||
|
|
No ``<A HREF="../TkCmd/glob.htm">glob</A>'' expansion or other shell-like substitutions
|
||
|
|
are performed on the arguments to commands.
|
||
|
|
|
||
|
|
<H3><A NAME="M21">PORTABILITY ISSUES</A></H3>
|
||
|
|
<DL>
|
||
|
|
<P><DT><A NAME="M22"><B>Windows</B> (all versions)</A><DD>
|
||
|
|
Reading from or writing to a socket, using the ``<B>@ </B><I>fileId</I>''
|
||
|
|
notation, does not work. When reading from a socket, a 16-bit DOS
|
||
|
|
application will hang and a 32-bit application will return immediately with
|
||
|
|
end-of-file. When either type of application writes to a socket, the
|
||
|
|
information is instead sent to the console, if one is present, or is
|
||
|
|
discarded.
|
||
|
|
<P>
|
||
|
|
The Tk console text widget does not provide real standard IO capabilities.
|
||
|
|
Under Tk, when redirecting from standard input, all applications will see an
|
||
|
|
immediate end-of-file; information redirected to standard output or standard
|
||
|
|
error will be discarded.
|
||
|
|
<P>
|
||
|
|
Either forward or backward slashes are accepted as path separators for
|
||
|
|
arguments to Tcl commands. When executing an application, the path name
|
||
|
|
specified for the application may also contain forward or backward slashes
|
||
|
|
as path separators. Bear in mind, however, that most Windows applications
|
||
|
|
accept arguments with forward slashes only as option delimiters and
|
||
|
|
backslashes only in paths. Any arguments to an application that specify a
|
||
|
|
path name with forward slashes will not automatically be converted to use
|
||
|
|
the backslash character. If an argument contains forward slashes as the
|
||
|
|
path separator, it may or may not be recognized as a path name, depending on
|
||
|
|
the program.
|
||
|
|
<P>
|
||
|
|
Additionally, when calling a 16-bit DOS or Windows 3.X application, all path
|
||
|
|
names must use the short, cryptic, path format (e.g., using ``applba~1.def''
|
||
|
|
instead of ``applbakery.default'').
|
||
|
|
<P>
|
||
|
|
Two or more forward or backward slashes in a row in a path refer to a
|
||
|
|
network path. For example, a simple concatenation of the root directory
|
||
|
|
<B>c:/</B> with a subdirectory <B>/windows/system</B> will yield
|
||
|
|
<B>c://windows/system</B> (two slashes together), which refers to the mount
|
||
|
|
point called <B>system</B> on the machine called <B>windows</B> (and the
|
||
|
|
<B>c:/</B> is ignored), and is not equivalent to <B>c:/windows/system</B>,
|
||
|
|
which describes a directory on the current computer. The <B><A HREF="../TkCmd/file.htm">file join</A></B>
|
||
|
|
command should be used to concatenate path components.
|
||
|
|
<P><DT><A NAME="M23"><B>Windows NT</B></A><DD>
|
||
|
|
When attempting to execute an application, <B>exec</B> first searches for the
|
||
|
|
name as it was specified. Then, in order, <B>.com</B>, <B>.exe</B>, and <B>.bat</B>
|
||
|
|
are appended to the end of the specified name and it searches for
|
||
|
|
the longer name. If a directory name was not specified as part of the
|
||
|
|
application name, the following directories are automatically searched in
|
||
|
|
order when attempting to locate the application:
|
||
|
|
<P>
|
||
|
|
<DL><P><DD>
|
||
|
|
The directory from which the Tcl executable was loaded.
|
||
|
|
<BR>
|
||
|
|
The current directory.
|
||
|
|
<BR>
|
||
|
|
The Windows NT 32-bit system directory.
|
||
|
|
<BR>
|
||
|
|
The Windows NT 16-bit system directory.
|
||
|
|
<BR>
|
||
|
|
The Windows NT home directory.
|
||
|
|
<BR>
|
||
|
|
The directories listed in the path.
|
||
|
|
</DL>
|
||
|
|
<P>
|
||
|
|
In order to execute the shell builtin commands like <B>dir</B> and <B>copy</B>,
|
||
|
|
the caller must prepend ``<B>cmd.exe /c </B>'' to the desired command.
|
||
|
|
<P>
|
||
|
|
<P><DT><A NAME="M24"><B>Windows 95</B></A><DD>
|
||
|
|
When attempting to execute an application, <B>exec</B> first searches for the
|
||
|
|
name as it was specified. Then, in order, <B>.com</B>, <B>.exe</B>, and <B>.bat</B>
|
||
|
|
are appended to the end of the specified name and it searches for
|
||
|
|
the longer name. If a directory name was not specified as part of the
|
||
|
|
application name, the following directories are automatically searched in
|
||
|
|
order when attempting to locate the application:
|
||
|
|
<P>
|
||
|
|
<DL><P><DD>
|
||
|
|
The directory from which the Tcl executable was loaded.
|
||
|
|
<BR>
|
||
|
|
The current directory.
|
||
|
|
<BR>
|
||
|
|
The Windows 95 system directory.
|
||
|
|
<BR>
|
||
|
|
The Windows 95 home directory.
|
||
|
|
<BR>
|
||
|
|
The directories listed in the path.
|
||
|
|
</DL>
|
||
|
|
<P>
|
||
|
|
In order to execute the shell builtin commands like <B>dir</B> and <B>copy</B>,
|
||
|
|
the caller must prepend ``<B>command.com /c </B>'' to the desired command.
|
||
|
|
<P>
|
||
|
|
Once a 16-bit DOS application has read standard input from a console and
|
||
|
|
then quit, all subsequently run 16-bit DOS applications will see the
|
||
|
|
standard input as already closed. 32-bit applications do not have this
|
||
|
|
problem and will run correctly, even after a 16-bit DOS application thinks
|
||
|
|
that standard input is closed. There is no known workaround for this bug
|
||
|
|
at this time.
|
||
|
|
<P>
|
||
|
|
Redirection between the <B>NUL:</B> device and a 16-bit application does not
|
||
|
|
always work. When redirecting from <B>NUL:</B>, some applications may hang,
|
||
|
|
others will get an infinite stream of ``0x01'' bytes, and some will actually
|
||
|
|
correctly get an immediate end-of-file; the behavior seems to depend upon
|
||
|
|
something compiled into the application itself. When redirecting greater than
|
||
|
|
4K or so to <B>NUL:</B>, some applications will hang. The above problems do not
|
||
|
|
happen with 32-bit applications.
|
||
|
|
<P>
|
||
|
|
All DOS 16-bit applications are run synchronously. All standard input from
|
||
|
|
a pipe to a 16-bit DOS application is collected into a temporary file; the
|
||
|
|
other end of the pipe must be closed before the 16-bit DOS application
|
||
|
|
begins executing. All standard output or error from a 16-bit DOS
|
||
|
|
application to a pipe is collected into temporary files; the application
|
||
|
|
must terminate before the temporary files are redirected to the next stage
|
||
|
|
of the pipeline. This is due to a workaround for a Windows 95 bug in the
|
||
|
|
implementation of pipes, and is how the standard Windows 95 DOS shell
|
||
|
|
handles pipes itself.
|
||
|
|
<P>
|
||
|
|
Certain applications, such as <B>command.com</B>, should not be executed
|
||
|
|
interactively. Applications which directly access the console window,
|
||
|
|
rather than reading from their standard input and writing to their standard
|
||
|
|
output may fail, hang Tcl, or even hang the system if their own private
|
||
|
|
console window is not available to them.
|
||
|
|
<P><DT><A NAME="M25"><B>Macintosh</B></A><DD>
|
||
|
|
The <B>exec</B> command is not implemented and does not exist under Macintosh.
|
||
|
|
<P><DT><A NAME="M26"><B>Unix</B></A><DD>
|
||
|
|
The <B>exec</B> command is fully functional and works as described.
|
||
|
|
|
||
|
|
<P></DL>
|
||
|
|
<H3><A NAME="M27">SEE ALSO</A></H3>
|
||
|
|
<B><A HREF="../TkCmd/error.htm">error</A></B>, <B><A HREF="../TkCmd/open.htm">open</A></B>
|
||
|
|
<H3><A NAME="M28">KEYWORDS</A></H3>
|
||
|
|
<A href="../Keywords/E.htm#execute">execute</A>, <A href="../Keywords/P.htm#pipeline">pipeline</A>, <A href="../Keywords/R.htm#redirection">redirection</A>, <A href="../Keywords/S.htm#subprocess">subprocess</A>
|
||
|
|
<HR><PRE>
|
||
|
|
<A HREF="../copyright.htm">Copyright</A> © 1993 The Regents of the University of California.
|
||
|
|
<A HREF="../copyright.htm">Copyright</A> © 1994-1996 Sun Microsystems, Inc.
|
||
|
|
<A HREF="../copyright.htm">Copyright</A> © 1995-1997 Roger E. Critchlow Jr.</PRE>
|
||
|
|
</BODY></HTML>
|