diff options
Diffstat (limited to 'doc/exec.n')
| -rw-r--r-- | doc/exec.n | 194 |
1 files changed, 114 insertions, 80 deletions
@@ -1,12 +1,13 @@ '\" '\" 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. '\" .so man.macros -.TH exec n 7.6 Tcl "Tcl Built-In Commands" +.TH exec n 8.5 Tcl "Tcl Built-In Commands" .BS '\" Note: do not modify the .SH NAME line immediately below! .SH NAME @@ -28,6 +29,12 @@ they are treated as command-line switches and are not part 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. @@ -40,76 +47,84 @@ 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 @@ -118,15 +133,23 @@ 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. +in the pipeline, +.VS 8.5 +unless +.QW 2>@1 +was specified, in which case standard error is included as well. +.VE 8.5 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 +.VS 8.5 +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 @@ -135,22 +158,27 @@ 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. @@ -162,26 +190,28 @@ 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. - -.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 @@ -192,12 +222,16 @@ 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. -.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 \fIfileName \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 @@ -206,25 +240,25 @@ point called \fBsystem\fR on the machine called \fBwindows\fR (and the \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 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 communicating with a TUI application. -.sp .RE .TP \fBWindows NT\fR @@ -235,26 +269,24 @@ the name as it was specified. Then, in order, \fB.com\fR, \fB.exe\fR, and 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 The directory from which the Tcl executable was loaded. -.br +.IP \(bu The current directory. -.br +.IP \(bu The Windows NT 32-bit system directory. -.br +.IP \(bu The Windows NT 16-bit system directory. -.br +.IP \(bu The Windows NT home directory. -.br +.IP \(bu The directories listed in the path. -.RE -.sp +.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. -.sp .RE .TP \fBWindows 9x\fR @@ -265,39 +297,42 @@ the name as it was specified. Then, in order, \fB.com\fR, \fB.exe\fR, and 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 The directory from which the Tcl executable was loaded. -.br +.IP \(bu The current directory. -.br +.IP \(bu The Windows 9x system directory. -.br +.IP \(bu The Windows 9x home directory. -.br +.IP \(bu The directories listed in the path. .RE -.sp +.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. -.sp +.PP 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 +.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 happen with 32-bit applications. -.sp +.PP 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 @@ -307,7 +342,7 @@ 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 +.PP 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 @@ -317,7 +352,6 @@ console window is not available to them. .TP \fBUnix\fR\0\0\0\0\0\0\0 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 @@ -327,13 +361,14 @@ To execute a simple program and get its result: .CE .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 what the contents -of the global \fBerrorCode\fR variable is if you have an error: +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: .CS set status 0 -if {[catch {\fBexec\fR grep foo bar.txt} results]} { - if {[lindex $::errorCode 0] eq "CHILDSTATUS"} { - set status [lindex $::errorCode 2] +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 } @@ -356,9 +391,8 @@ remember that Tcl does not handle globbing or expand things into multiple arguments by default. Instead you should write things like this: .CS -eval [list \fBexec\fR ls -l] [glob *.tcl] +\fBexec\fR ls -l {*}[glob *.tcl] .CE -.PP .SH "WINDOWS EXAMPLES" Here are some examples of the use of the \fBexec\fR command on Windows. .PP @@ -392,15 +426,15 @@ 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: .CS -eval [list \fBexec\fR] [auto_execok dir] [list *.tcl] +\fBexec\fR {*}[auto_execok dir] *.tcl .CE - .SH "SEE ALSO" error(n), open(n) - .SH KEYWORDS execute, pipeline, redirection, subprocess |