diff options
Diffstat (limited to 'doc/exec.n')
| -rw-r--r-- | doc/exec.n | 252 |
1 files changed, 173 insertions, 79 deletions
@@ -6,18 +6,15 @@ '\" 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 1.16 2007/07/04 13:51:29 dkf Exp $ -'\" -.so man.macros .TH exec n 8.5 Tcl "Tcl Built-In Commands" +.so man.macros .BS '\" Note: do not modify the .SH NAME line immediately below! .SH NAME 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 @@ -32,16 +29,17 @@ of the pipeline specification. The following switches are currently supported: .TP 13 \fB\-ignorestderr\fR -.VS 8.5 +. Stops the \fBexec\fR command from treating the output of messages to the pipeline's standard error channel as an error case. -.VE 8.5 .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 @@ -49,81 +47,99 @@ 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 -2>@1\0 +\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 ->&@\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. Both standard output from the last command and standard error from @@ -132,22 +148,18 @@ The file must have been opened for writing. .PP If standard output has not been redirected then the \fBexec\fR command returns the standard output from the last command -in the pipeline, -.VS 8.5 -unless ``2>@1'' was specified, in which case -standard error is included as well. -.VE 8.5 +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 -\fB-errorcode\fR return option 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 -.VS 8.5 +standard error is not redirected and \fB\-ignorestderr\fR is not specified, -.VE 8.5 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 @@ -156,22 +168,27 @@ output. 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. @@ -183,13 +200,16 @@ 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 ``glob'' expansion or other shell-like substitutions +No +.QW glob +expansion or other shell-like substitutions are performed on the arguments to commands. .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 @@ -214,9 +234,13 @@ path separator, it may or may not be recognized as a path name, depending on the program. .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. +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 @@ -229,15 +253,11 @@ command should be used to concatenate path components. .PP Note that there are two general types of Win32 console applications: .RS -.TP -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. -.TP -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 from Windows 2000. These types of applications are not common in a windows @@ -260,21 +280,22 @@ 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: .RS -.IP \(bu +.IP \(bu 3 The directory from which the Tcl executable was loaded. -.IP \(bu +.IP \(bu 3 The current directory. -.IP \(bu +.IP \(bu 3 The Windows NT 32-bit system directory. -.IP \(bu +.IP \(bu 3 The Windows NT 16-bit system directory. -.IP \(bu +.IP \(bu 3 The Windows NT home directory. -.IP \(bu +.IP \(bu 3 The directories listed in the path. .PP In order to execute shell built-in commands like \fBdir\fR and \fBcopy\fR, -the caller must prepend the desired command with ``\fBcmd.exe /c\0\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 @@ -287,19 +308,22 @@ 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: .RS -.IP \(bu +.IP \(bu 3 The directory from which the Tcl executable was loaded. -.IP \(bu +.IP \(bu 3 The current directory. -.IP \(bu +.IP \(bu 3 The Windows 9x system directory. -.IP \(bu +.IP \(bu 3 The Windows 9x home directory. -.IP \(bu +.IP \(bu 3 The directories listed in the path. +.RE +.RS .PP In order to execute shell built-in commands like \fBdir\fR and \fBcopy\fR, -the caller must prepend the desired command with ``\fBcommand.com /c\0\fR'' +the caller must prepend the desired command with +.QW "\fBcommand.com /c\0\fR" because built-in commands are not implemented using executables. .PP Once a 16-bit DOS application has read standard input from a console and @@ -311,7 +335,9 @@ at this time. .PP 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 +others will get an infinite stream of +.QW 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 @@ -334,73 +360,122 @@ output may fail, hang Tcl, or even hang the system if their own private console window is not available to them. .RE .TP -\fBUnix\fR\0\0\0\0\0\0\0 +\fBUnix\fR (including Mac OS X) +. The \fBexec\fR command is fully functional and works as described. .SH "UNIX EXAMPLES" -Here are some examples of the use of the \fBexec\fR command on Unix. .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: +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 kind of unexpected failure - } + 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" -Here are some examples of the use of the \fBexec\fR command on Windows. .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 @@ -410,13 +485,32 @@ 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 "internal" commands like +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: |