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try - try - Trap and process errors and exceptions

Table Of Contents


package require Tcl 8.5
package require try ?1?

::try body ?handler...? ?finally script?


This package provides a forward-compatibility implementation of Tcl 8.6's try/finally command (TIP 329), for Tcl 8.5. The code was directly pulled from Tcl 8.6 revision ?, when try/finally was implemented as Tcl procedure instead of in C.


Ensure that a file is closed no matter what:

set f [open /some/file/name a]
try {
    puts \$f "some message"
    # ...
} finally {
    close \$f

Handle different reasons for a file to not be openable for reading:

try {
    set f [open /some/file/name]
} trap {POSIX EISDIR} {} {
    puts "failed to open /some/file/name: it's a directory"
} trap {POSIX ENOENT} {} {
    puts "failed to open /some/file/name: it doesn't exist"

Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category try of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide unified diffs, i.e the output of diff -u.

Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.


catch(n), error(n), return(n), throw(n)


cleanup, error, exception, final, resource management




Copyright © 2008 Donal K. Fellows, BSD licensed