'\"
'\" Copyright (c) 1993 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
+'\" Copyright (c) 2006 Donal K. Fellows.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
-'\" RCS: @(#) $Id: exec.n,v 1.6 2002/04/23 19:06:10 hobbs Exp $
-'\"
-'\" The definitions below are for supplemental macros used in Tcl/Tk
-'\" manual entries.
-'\"
-'\" .AP type name in/out ?indent?
-'\" Start paragraph describing an argument to a library procedure.
-'\" type is type of argument (int, etc.), in/out is either "in", "out",
-'\" or "in/out" to describe whether procedure reads or modifies arg,
-'\" and indent is equivalent to second arg of .IP (shouldn't ever be
-'\" needed; use .AS below instead)
-'\"
-'\" .AS ?type? ?name?
-'\" Give maximum sizes of arguments for setting tab stops. Type and
-'\" name are examples of largest possible arguments that will be passed
-'\" to .AP later. If args are omitted, default tab stops are used.
-'\"
-'\" .BS
-'\" Start box enclosure. From here until next .BE, everything will be
-'\" enclosed in one large box.
-'\"
-'\" .BE
-'\" End of box enclosure.
-'\"
-'\" .CS
-'\" Begin code excerpt.
-'\"
-'\" .CE
-'\" End code excerpt.
-'\"
-'\" .VS ?version? ?br?
-'\" Begin vertical sidebar, for use in marking newly-changed parts
-'\" of man pages. The first argument is ignored and used for recording
-'\" the version when the .VS was added, so that the sidebars can be
-'\" found and removed when they reach a certain age. If another argument
-'\" is present, then a line break is forced before starting the sidebar.
-'\"
-'\" .VE
-'\" End of vertical sidebar.
-'\"
-'\" .DS
-'\" Begin an indented unfilled display.
-'\"
-'\" .DE
-'\" End of indented unfilled display.
-'\"
-'\" .SO
-'\" Start of list of standard options for a Tk widget. The
-'\" options follow on successive lines, in four columns separated
-'\" by tabs.
-'\"
-'\" .SE
-'\" End of list of standard options for a Tk widget.
-'\"
-'\" .OP cmdName dbName dbClass
-'\" Start of description of a specific option. cmdName gives the
-'\" option's name as specified in the class command, dbName gives
-'\" the option's name in the option database, and dbClass gives
-'\" the option's class in the option database.
-'\"
-'\" .UL arg1 arg2
-'\" Print arg1 underlined, then print arg2 normally.
-'\"
-'\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $
-'\"
-'\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
+.TH exec n 8.5 Tcl "Tcl Built-In Commands"
+.\" The -*- nroff -*- definitions below are for supplemental macros used
+.\" in Tcl/Tk manual entries.
+.\"
+.\" .AP type name in/out ?indent?
+.\" Start paragraph describing an argument to a library procedure.
+.\" type is type of argument (int, etc.), in/out is either "in", "out",
+.\" or "in/out" to describe whether procedure reads or modifies arg,
+.\" and indent is equivalent to second arg of .IP (shouldn't ever be
+.\" needed; use .AS below instead)
+.\"
+.\" .AS ?type? ?name?
+.\" Give maximum sizes of arguments for setting tab stops. Type and
+.\" name are examples of largest possible arguments that will be passed
+.\" to .AP later. If args are omitted, default tab stops are used.
+.\"
+.\" .BS
+.\" Start box enclosure. From here until next .BE, everything will be
+.\" enclosed in one large box.
+.\"
+.\" .BE
+.\" End of box enclosure.
+.\"
+.\" .CS
+.\" Begin code excerpt.
+.\"
+.\" .CE
+.\" End code excerpt.
+.\"
+.\" .VS ?version? ?br?
+.\" Begin vertical sidebar, for use in marking newly-changed parts
+.\" of man pages. The first argument is ignored and used for recording
+.\" the version when the .VS was added, so that the sidebars can be
+.\" found and removed when they reach a certain age. If another argument
+.\" is present, then a line break is forced before starting the sidebar.
+.\"
+.\" .VE
+.\" End of vertical sidebar.
+.\"
+.\" .DS
+.\" Begin an indented unfilled display.
+.\"
+.\" .DE
+.\" End of indented unfilled display.
+.\"
+.\" .SO ?manpage?
+.\" Start of list of standard options for a Tk widget. The manpage
+.\" argument defines where to look up the standard options; if
+.\" omitted, defaults to "options". The options follow on successive
+.\" lines, in three columns separated by tabs.
+.\"
+.\" .SE
+.\" End of list of standard options for a Tk widget.
+.\"
+.\" .OP cmdName dbName dbClass
+.\" Start of description of a specific option. cmdName gives the
+.\" option's name as specified in the class command, dbName gives
+.\" the option's name in the option database, and dbClass gives
+.\" the option's class in the option database.
+.\"
+.\" .UL arg1 arg2
+.\" Print arg1 underlined, then print arg2 normally.
+.\"
+.\" .QW arg1 ?arg2?
+.\" Print arg1 in quotes, then arg2 normally (for trailing punctuation).
+.\"
+.\" .PQ arg1 ?arg2?
+.\" Print an open parenthesis, arg1 in quotes, then arg2 normally
+.\" (for trailing punctuation) and then a closing parenthesis.
+.\"
+.\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
.if t .wh -1.3i ^B
.nr ^l \n(.l
.ad b
-'\" # Start an argument description
+.\" # Start an argument description
.de AP
.ie !"\\$4"" .TP \\$4
.el \{\
.\}
.ta \\n()Au \\n()Bu
.ie !"\\$3"" \{\
-\&\\$1 \\fI\\$2\\fP (\\$3)
+\&\\$1 \\fI\\$2\\fP (\\$3)
.\".b
.\}
.el \{\
.\}
.\}
..
-'\" # define tabbing values for .AP
+.\" # define tabbing values for .AP
.de AS
.nr )A 10n
.if !"\\$1"" .nr )A \\w'\\$1'u+3n
.nr )C \\n()Bu+\\w'(in/out)'u+2n
..
.AS Tcl_Interp Tcl_CreateInterp in/out
-'\" # BS - start boxed text
-'\" # ^y = starting y location
-'\" # ^b = 1
+.\" # BS - start boxed text
+.\" # ^y = starting y location
+.\" # ^b = 1
.de BS
.br
.mk ^y
.if n \l'\\n(.lu\(ul'
.if n .fi
..
-'\" # BE - end boxed text (draw box now)
+.\" # BE - end boxed text (draw box now)
.de BE
.nf
.ti 0
.br
.nr ^b 0
..
-'\" # VS - start vertical sidebar
-'\" # ^Y = starting y location
-'\" # ^v = 1 (for troff; for nroff this doesn't matter)
+.\" # VS - start vertical sidebar
+.\" # ^Y = starting y location
+.\" # ^v = 1 (for troff; for nroff this doesn't matter)
.de VS
.if !"\\$2"" .br
.mk ^Y
.ie n 'mc \s12\(br\s0
.el .nr ^v 1u
..
-'\" # VE - end of vertical sidebar
+.\" # VE - end of vertical sidebar
.de VE
.ie n 'mc
.el \{\
.\}
.nr ^v 0
..
-'\" # Special macro to handle page bottom: finish off current
-'\" # box/sidebar if in box/sidebar mode, then invoked standard
-'\" # page bottom macro.
+.\" # Special macro to handle page bottom: finish off current
+.\" # box/sidebar if in box/sidebar mode, then invoked standard
+.\" # page bottom macro.
.de ^B
.ev 2
'ti 0
.mk ^Y
.\}
..
-'\" # DS - begin display
+.\" # DS - begin display
.de DS
.RS
.nf
.sp
..
-'\" # DE - end display
+.\" # DE - end display
.de DE
.fi
.RE
.sp
..
-'\" # SO - start of list of standard options
+.\" # SO - start of list of standard options
.de SO
+'ie '\\$1'' .ds So \\fBoptions\\fR
+'el .ds So \\fB\\$1\\fR
.SH "STANDARD OPTIONS"
.LP
.nf
.ta 5.5c 11c
.ft B
..
-'\" # SE - end of list of standard options
+.\" # SE - end of list of standard options
.de SE
.fi
.ft R
.LP
-See the \\fBoptions\\fR manual entry for details on the standard options.
+See the \\*(So manual entry for details on the standard options.
..
-'\" # OP - start of full description for a single option
+.\" # OP - start of full description for a single option
.de OP
.LP
.nf
.fi
.IP
..
-'\" # CS - begin code excerpt
+.\" # CS - begin code excerpt
.de CS
.RS
.nf
.ta .25i .5i .75i 1i
..
-'\" # CE - end code excerpt
+.\" # CE - end code excerpt
.de CE
.fi
.RE
..
+.\" # UL - underline word
.de UL
\\$1\l'|0\(ul'\\$2
..
-.TH exec n 7.6 Tcl "Tcl Built-In Commands"
+.\" # QW - apply quotation marks to word
+.de QW
+.ie '\\*(lq'"' ``\\$1''\\$2
+.\"" fix emacs highlighting
+.el \\*(lq\\$1\\*(rq\\$2
+..
+.\" # PQ - apply parens and quotation marks to word
+.de PQ
+.ie '\\*(lq'"' (``\\$1''\\$2)\\$3
+.\"" fix emacs highlighting
+.el (\\*(lq\\$1\\*(rq\\$2)\\$3
+..
+.\" # QR - quoted range
+.de QR
+.ie '\\*(lq'"' ``\\$1''\\-``\\$2''\\$3
+.\"" fix emacs highlighting
+.el \\*(lq\\$1\\*(rq\\-\\*(lq\\$2\\*(rq\\$3
+..
+.\" # MT - "empty" string
+.de MT
+.QW ""
+..
.BS
'\" Note: do not modify the .SH NAME line immediately below!
.SH NAME
-exec \- Invoke subprocess(es)
+exec \- Invoke subprocesses
.SH SYNOPSIS
-\fBexec \fR?\fIswitches\fR? \fIarg \fR?\fIarg ...\fR?
+\fBexec \fR?\fIswitches\fR? \fIarg \fR?\fIarg ...\fR? ?\fB&\fR?
.BE
-
.SH DESCRIPTION
.PP
This command treats its arguments as the specification
of the pipeline specification. The following switches are
currently supported:
.TP 13
+\fB\-ignorestderr\fR
+.
+Stops the \fBexec\fR command from treating the output of messages to the
+pipeline's standard error channel as an error case.
+.TP 13
\fB\-keepnewline\fR
+.
Retains a trailing newline in the pipeline's output.
Normally a trailing newline will be deleted.
.TP 13
\fB\-\|\-\fR
+.
Marks the end of switches. The argument following this one will
be treated as the first \fIarg\fR even if it starts with a \fB\-\fR.
.PP
-If an \fIarg\fR (or pair of \fIarg\fR's) has one of the forms
+If an \fIarg\fR (or pair of \fIarg\fRs) has one of the forms
described below then it is used by \fBexec\fR 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 ``< \fIfileName\fR'' \fIfileName\fR may either be in a
-separate argument from ``<'' or in the same argument with no
-intervening space (i.e. ``<\fIfileName\fR'').
+such as
+.QW "\fB<\fR \fIfileName\fR" ,
+\fIfileName\fR may either be in a separate argument from
+.QW \fB<\fR
+or in the same argument with no intervening space (i.e.
+.QW \fB<\fIfileName\fR ).
.TP 15
-|
+\fB|\fR
+.
Separates distinct commands in the pipeline. The standard output
of the preceding command will be piped into the standard input
of the next command.
.TP 15
-|&
+\fB|&\fR
+.
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 >&.
.TP 15
-<\0\fIfileName\fR
+\fB<\0\fIfileName\fR
+.
The file named by \fIfileName\fR is opened and used as the standard
input for the first command in the pipeline.
.TP 15
-<@\0\fIfileId\fR
+\fB<@\0\fIfileId\fR
+.
\fIFileId\fR must be the identifier for an open file, such as the return
value from a previous call to \fBopen\fR.
It is used as the standard input for the first command in the pipeline.
\fIFileId\fR must have been opened for reading.
.TP 15
-<<\0\fIvalue\fR
+\fB<<\0\fIvalue\fR
+.
\fIValue\fR is passed to the first command as its standard input.
.TP 15
->\0\fIfileName\fR
+\fB>\0\fIfileName\fR
+.
Standard output from the last command is redirected to the file named
\fIfileName\fR, overwriting its previous contents.
.TP 15
-2>\0\fIfileName\fR
+\fB2>\0\fIfileName\fR
+.
Standard error from all commands in the pipeline is redirected to the
file named \fIfileName\fR, overwriting its previous contents.
.TP 15
->&\0\fIfileName\fR
+\fB>&\0\fIfileName\fR
+.
Both standard output from the last command and standard error from all
commands are redirected to the file named \fIfileName\fR, overwriting
its previous contents.
.TP 15
->>\0\fIfileName\fR
+\fB>>\0\fIfileName\fR
+.
Standard output from the last command is
redirected to the file named \fIfileName\fR, appending to it rather
than overwriting it.
.TP 15
-2>>\0\fIfileName\fR
+\fB2>>\0\fIfileName\fR
+.
Standard error from all commands in the pipeline is
redirected to the file named \fIfileName\fR, appending to it rather
than overwriting it.
.TP 15
->>&\0\fIfileName\fR
+\fB>>&\0\fIfileName\fR
+.
Both standard output from the last command and standard error from
all commands are redirected to the file named \fIfileName\fR,
appending to it rather than overwriting it.
.TP 15
->@\0\fIfileId\fR
+\fB>@\0\fIfileId\fR
+.
\fIFileId\fR must be the identifier for an open file, such as the return
value from a previous call to \fBopen\fR.
Standard output from the last command is redirected to \fIfileId\fR's
file, which must have been opened for writing.
.TP 15
-2>@\0\fIfileId\fR
+\fB2>@\0\fIfileId\fR
+.
\fIFileId\fR must be the identifier for an open file, such as the return
value from a previous call to \fBopen\fR.
Standard error from all commands in the pipeline is
redirected to \fIfileId\fR's file.
The file must have been opened for writing.
.TP 15
->&@\0\fIfileId\fR
+\fB2>@1\0\fR
+.
+Standard error from all commands in the pipeline is redirected to the
+command result. This operator is only valid at the end of the command
+pipeline.
+.TP 15
+\fB>&@\0\fIfileId\fR
+.
\fIFileId\fR must be the identifier for an open file, such as the return
value from a previous call to \fBopen\fR.
Both standard output from the last command and standard error from
.PP
If standard output has not been redirected then the \fBexec\fR
command returns the standard output from the last command
-in the pipeline.
+in the pipeline, unless
+.QW 2>@1
+was specified, in which case standard error is included as well.
If any of the commands in the pipeline exit abnormally or
are killed or suspended, then \fBexec\fR will return an error
and the error message will include the pipeline's output followed by
error messages describing the abnormal terminations; the
-\fBerrorCode\fR variable will contain additional information
+\fB\-errorcode\fR return option 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,
+standard error is not redirected
+and \fB\-ignorestderr\fR is not specified,
then \fBexec\fR 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
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
+This is consistent with other Tcl return values, which do not
normally end with newlines.
However, if \fB\-keepnewline\fR is specified then the trailing
newline is retained.
.PP
-If standard input isn't redirected with ``<'' or ``<<''
-or ``<@'' then the standard input for the first command in the
+If standard input is not redirected with
+.QW < ,
+.QW <<
+or
+.QW <@
+then the standard input for the first command in the
pipeline is taken from the application's current standard input.
.PP
-If the last \fIarg\fR is ``&'' then the pipeline will be
-executed in background.
+If the last \fIarg\fR is
+.QW &
+then the pipeline will be executed in background.
In this case the \fBexec\fR 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
+go to the application's standard output if it has not been
redirected, and error output from all of
the commands in the pipeline will go to the application's
standard error file unless redirected.
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 ``glob'' expansion or other shell-like substitutions
+No
+.QW glob
+expansion or other shell-like substitutions
are performed on the arguments to commands.
-
-.VS
.SH "PORTABILITY ISSUES"
.TP
\fBWindows\fR (all versions)
.
-Reading from or writing to a socket, using the ``\fB@\0\fIfileId\fR''
+Reading from or writing to a socket, using the
+.QW \fB@\0\fIfileId\fR
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.
-.sp
+.RS
+.PP
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.
-.sp
+.PP
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
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.
-.sp
+.PP
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''), which can be obtained with the
-\fBfile attributes $fileName -shortname\fR command.
-.sp
+names must use the short, cryptic, path format (e.g., using
+.QW applba~1.def
+instead of
+.QW applbakery.default ),
+which can be obtained with the
+.QW "\fBfile attributes\fI fileName \fB\-shortname\fR"
+command.
+.PP
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
\fBc:/\fR with a subdirectory \fB/windows/system\fR will yield
\fBc:/\fR is ignored), and is not equivalent to \fBc:/windows/system\fR,
which describes a directory on the current computer. The \fBfile join\fR
command should be used to concatenate path components.
-.sp
-.RS
+.PP
Note that there are two general types of Win32 console applications:
.RS
-1) CLI -- CommandLine Interface, simple stdio exchange. \fBnetstat.exe\fR for
+.IP [1]
+CLI \(em CommandLine Interface, simple stdio exchange. \fBnetstat.exe\fR for
example.
-.br
-2) TUI -- Textmode User Interface, any application that accesses the console
+.IP [2]
+TUI \(em Textmode User Interface, any application that accesses the console
API for doing such things as cursor movement, setting text color, detecting
-key presses and mouse movement, etc... An example would be \fBtelnet.exe\fR
+key presses and mouse movement, etc. An example would be \fBtelnet.exe\fR
from Windows 2000. These types of applications are not common in a windows
environment, but do exist.
.RE
+.PP
\fBexec\fR will not work well with TUI applications when a console is not
present, as is done when launching applications under wish. It is desirable
to have console applications hidden and detached. This is a designed-in
limitation as \fBexec\fR wants to communicate over pipes. The Expect
-extension addresses this issue when communication between a TUI application
-is desired.
-.sp
-.RE
-.TP
-\fBWindows NT\fR
-.
+extension addresses this issue when communicating with a TUI application.
+.PP
When attempting to execute an application, \fBexec\fR first searches for
the name as it was specified. Then, in order, \fB.com\fR, \fB.exe\fR, and
\fB.bat\fR 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:
-.sp
-.RS
-.RS
+.IP \(bu 3
The directory from which the Tcl executable was loaded.
-.br
+.IP \(bu 3
The current directory.
-.br
+.IP \(bu 3
The Windows NT 32-bit system directory.
-.br
+.IP \(bu 3
The Windows NT 16-bit system directory.
-.br
+.IP \(bu 3
The Windows NT home directory.
-.br
+.IP \(bu 3
The directories listed in the path.
-.RE
-.sp
-In order to execute the shell builtin commands like \fBdir\fR and \fBcopy\fR,
-the caller must prepend ``\fBcmd.exe /c\0\fR'' to the desired command.
-.sp
+.PP
+In order to execute shell built-in commands like \fBdir\fR and \fBcopy\fR,
+the caller must prepend the desired command with
+.QW "\fBcmd.exe /c\0\fR"
+because built-in commands are not implemented using executables.
.RE
.TP
-\fBWindows 95\fR
+\fBUnix\fR (including Mac OS X)
.
-When attempting to execute an application, \fBexec\fR first searches for
-the name as it was specified. Then, in order, \fB.com\fR, \fB.exe\fR, and
-\fB.bat\fR 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:
-.sp
-.RS
-.RS
-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.
-.RE
-.sp
-In order to execute the shell builtin commands like \fBdir\fR and \fBcopy\fR,
-the caller must prepend ``\fBcommand.com /c\0\fR'' to the desired command.
-.sp
-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.
-.sp
-Redirection between the \fBNUL:\fR device and a 16-bit application does not
-always work. When redirecting from \fBNUL:\fR, 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 \fBNUL:\fR, some applications will hang. The above problems do not
-happen with 32-bit applications.
-.sp
-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.
-.sp
-Certain applications, such as \fBcommand.com\fR, 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.
-.RE
-.TP
-\fBMacintosh\fR
-The \fBexec\fR command is not implemented and does not exist under Macintosh.
-.TP
-\fBUnix\fR\0\0\0\0\0\0\0
The \fBexec\fR command is fully functional and works as described.
+.SH "UNIX EXAMPLES"
+.PP
+Here are some examples of the use of the \fBexec\fR command on Unix.
+To execute a simple program and get its result:
+.PP
+.CS
+\fBexec\fR uname -a
+.CE
+.SS "WORKING WITH NON-ZERO RESULTS"
+.PP
+To execute a program that can return a non-zero result, you should
+wrap the call to \fBexec\fR in \fBcatch\fR and check the contents
+of the \fB\-errorcode\fR return option if you have an error:
+.PP
+.CS
+set status 0
+if {[catch {\fBexec\fR grep foo bar.txt} results options]} {
+ set details [dict get $options -errorcode]
+ if {[lindex $details 0] eq "CHILDSTATUS"} {
+ set status [lindex $details 2]
+ } else {
+ # Some other error; regenerate it to let caller handle
+ return -options $options -level 0 $results
+ }
+}
+.CE
+.VS 8.6
+.PP
+This is more easily written using the \fBtry\fR command, as that makes
+it simpler to trap specific types of errors. This is
+done using code like this:
+.PP
+.CS
+try {
+ set results [\fBexec\fR grep foo bar.txt]
+ set status 0
+} trap CHILDSTATUS {results options} {
+ set status [lindex [dict get $options -errorcode] 2]
+}
+.CE
+.VE 8.6
+.SS "WORKING WITH QUOTED ARGUMENTS"
+.PP
+When translating a command from a Unix shell invocation, care should
+be taken over the fact that single quote characters have no special
+significance to Tcl. Thus:
+.PP
+.CS
+awk '{sum += $1} END {print sum}' numbers.list
+.CE
+.PP
+would be translated into something like:
+.PP
+.CS
+\fBexec\fR awk {{sum += $1} END {print sum}} numbers.list
+.CE
+.SS "WORKING WITH GLOBBING"
+.PP
+If you are converting invocations involving shell globbing, you should
+remember that Tcl does not handle globbing or expand things into
+multiple arguments by default. Instead you should write things like
+this:
+.PP
+.CS
+\fBexec\fR ls -l {*}[glob *.tcl]
+.CE
+.SS "WORKING WITH USER-SUPPLIED SHELL SCRIPT FRAGMENTS"
+.PP
+One useful technique can be to expose to users of a script the ability
+to specify a fragment of shell script to execute that will have some
+data passed in on standard input that was produced by the Tcl program.
+This is a common technique for using the \fIlpr\fR program for
+printing. By far the simplest way of doing this is to pass the user's
+script to the user's shell for processing, as this avoids a lot of
+complexity with parsing other languages.
+.PP
+.CS
+set lprScript [\fIget from user...\fR]
+set postscriptData [\fIgenerate somehow...\fR]
+\fBexec\fR $env(SHELL) -c $lprScript << $postscriptData
+.CE
+.SH "WINDOWS EXAMPLES"
+.PP
+Here are some examples of the use of the \fBexec\fR command on Windows.
+To start an instance of \fInotepad\fR editing a file without waiting
+for the user to finish editing the file:
+.PP
+.CS
+\fBexec\fR notepad myfile.txt &
+.CE
+.PP
+To print a text file using \fInotepad\fR:
+.PP
+.CS
+\fBexec\fR notepad /p myfile.txt
+.CE
+.SS "WORKING WITH CONSOLE PROGRAMS"
+.PP
+If a program calls other programs, such as is common with compilers,
+then you may need to resort to batch files to hide the console windows
+that sometimes pop up:
+.PP
+.CS
+\fBexec\fR cmp.bat somefile.c -o somefile
+.CE
+.PP
+With the file \fIcmp.bat\fR looking something like:
+.PP
+.CS
+@gcc %1 %2 %3 %4 %5 %6 %7 %8 %9
+.CE
+.SS "WORKING WITH COMMAND BUILT-INS"
+.PP
+Sometimes you need to be careful, as different programs may have the
+same name and be in the path. It can then happen that typing a command
+at the DOS prompt finds \fIa different program\fR than the same
+command run via \fBexec\fR. This is because of the (documented)
+differences in behaviour between \fBexec\fR and DOS batch files.
+.PP
+When in doubt, use the command \fBauto_execok\fR: it will return the
+complete path to the program as seen by the \fBexec\fR command. This
+applies especially when you want to run
+.QW internal
+commands like
+\fIdir\fR from a Tcl script (if you just want to list filenames, use
+the \fBglob\fR command.) To do that, use this:
+.PP
+.CS
+\fBexec\fR {*}[auto_execok dir] *.tcl
+.CE
+.SS "WORKING WITH NATIVE FILENAMES"
+.PP
+Many programs on Windows require filename arguments to be passed in with
+backslashes as pathname separators. This is done with the help of the
+\fBfile nativename\fR command. For example, to make a directory (on NTFS)
+encrypted so that only the current user can access it requires use of
+the \fICIPHER\fR command, like this:
+.PP
+.CS
+set secureDir "~/Desktop/Secure Directory"
+file mkdir $secureDir
+\fBexec\fR CIPHER /e /s:[file nativename $secureDir]
+.CE
.SH "SEE ALSO"
-error(n), open(n)
-
+error(n), file(n), open(n)
.SH KEYWORDS
execute, pipeline, redirection, subprocess
+'\" Local Variables:
+'\" mode: nroff
+'\" End:
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