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Diffstat (limited to 'doc/exec.n')
| -rw-r--r-- | doc/exec.n | 84 |
1 files changed, 82 insertions, 2 deletions
@@ -5,7 +5,7 @@ '\" 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 1.7 2004/03/17 18:14:12 das Exp $ +'\" RCS: @(#) $Id: exec.n,v 1.8 2004/04/22 12:48:25 dkf Exp $ '\" .so man.macros .TH exec n 7.6 Tcl "Tcl Built-In Commands" @@ -167,7 +167,6 @@ reachable from the current directory. No ``glob'' expansion or other shell-like substitutions are performed on the arguments to commands. -.VS .SH "PORTABILITY ISSUES" .TP \fBWindows\fR (all versions) @@ -319,6 +318,87 @@ console window is not available to them. \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. + +To execute a simple program and get its result: +.CS +exec uname -a +.CE + +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: +.CS +set status 0 +if {[catch {exec grep foo bar.txt} results]} { + if {[lindex $::errorCode 0] eq "CHILDSTATUS"} { + set status [lindex $::errorCode 2] + } else { + # Some kind of unexpected failure + } +} +.CE + +When translating a command from a Unix shell invokation, care should +be taken over the fact that single quote characters have no special +significance to Tcl. Thus: +.CS +awk '{sum += $1} END {print sum}' numbers.list +.CE +would be translated into something like: +.CS +exec awk {{sum += $1} END {print sum}} numbers.list +.CE + +If you are converting invokations 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: +.CS +exec ls -l {expand}[glob *.tcl] +.CE + +.SH "WINDOWS EXAMPLES" +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: +.CS +exec notepad myfile.txt & +.CE + +To print a text file using \fInotepad\fR: +.CS +exec notepad /p myfile.txt +.CE + +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: +.CS +exec cmp.bat somefile.c -o somefile +.CE +With the file \fIcmp.bat\fR looking something like: +.CS +@gcc %1 %2 %3 %4 %5 %6 %7 %8 %9 +.CE + +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. + +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 +\fIdir\fR from a Tcl script (if you just want to list filenames, use +the \fBglob\fR command.) To do that, use this: +.CS +exec {expand}[auto_execok dir] *.tcl +.CE + .SH "SEE ALSO" error(n), open(n) |