NAME<\/a> ______________________________________________________________________________<\/p>\n try \u2212 Trap and process errors and exceptions<\/p>\n try<\/b> body<\/i> ?handler…<\/i>? ?finally<\/b> script<\/i>? ______________________________________________________________________________<\/p>\n This command executes the script body<\/i> and, depending on what the outcome of that script is (normal exit, error, or some other exceptional result), runs a handler script to deal with the case. Once that has all happened, if the finally<\/b> clause is present, the script<\/i> it includes will be run and the result of the handler (or the body<\/i> if no handler matched) is allowed to continue to propagate. Note that the finally<\/b> clause is processed even if an error occurs and irrespective of which, if any, handler<\/i> is used.<\/p>\n The handler<\/i> clauses are each expressed as several words, and must have one of the following forms: This clause matches if the evaluation of body<\/i> completed with the exception code code<\/i>. The code<\/i> may be expressed as an integer or one of the following literal words: ok<\/b>, error<\/b>, return<\/b>, break<\/b>, or continue<\/b>. Those literals correspond to the integers 0 through 4 respectively.<\/p>\n trap<\/b> pattern variableList script<\/i><\/p>\n This clause matches if the evaluation of body<\/i> resulted in an error and the prefix of the \u2212errorcode<\/b> from the interpreter\u2019s status dictionary is equal to the pattern<\/i>. The number of prefix words taken from the \u2212errorcode<\/b> is equal to the list-length of pattern<\/i>, and inter-word spaces are normalized in both the \u2212errorcode<\/b> and pattern<\/i> before comparison.<\/p>\n The variableList<\/i> word in each handler<\/i> is always interpreted as a list of variable names. If the first word of the list is present and non-empty, it names a variable into which the result of the evaluation of body<\/i> (from the main try<\/b>) will be placed; this will contain the human-readable form of any errors. If the second word of the list is present and non-empty, it names a variable into which the options dictionary of the interpreter at the moment of completion of execution of body<\/i> will be placed.<\/p>\n The script<\/i> word of each handler<\/i> is also always interpreted the same: as a Tcl script to evaluate if the clause is matched. If script<\/i> is a literal \u201c\u2212\u201d and the handler<\/i> is not the last one, the script<\/i> of the following handler<\/i> is invoked instead (just like with the switch<\/b> command).<\/p>\n Note that handler<\/i> clauses are matched against in order, and that the first matching one is always selected. At most one handler<\/i> clause will selected. As a consequence, an on error<\/b> will mask any subsequent trap<\/b> in the try<\/b>. Also note that on error<\/b> is equivalent to trap {}<\/b>.<\/p>\n If an exception (i.e. any non-ok<\/b> result) occurs during the evaluation of either the handler<\/i> or the finally<\/b> clause, the original exception\u2019s status dictionary will be added to the new exception\u2019s status dictionary under the \u2212during<\/b> key.<\/p>\n Ensure that a file is closed no matter what:<\/p>\n set f [open \/some\/file\/name a] Handle different reasons for a file to not be openable for reading:<\/p>\n try<\/b> { catch(n), error(n), return(n), throw(n)<\/p>\n cleanup, error, exception, final, resource management<\/p>\n try \u2212 Trap and process errors and exceptions <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3783,1],"tags":[2635,2644],"class_list":["post-5949","post","type-post","status-publish","format-standard","hentry","category-n-comandos-tcl-tk","category-sin-categoria","tag-mann","tag-try"],"gutentor_comment":0,"_links":{"self":[{"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/posts\/5949","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/comments?post=5949"}],"version-history":[{"count":0,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/posts\/5949\/revisions"}],"wp:attachment":[{"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/media?parent=5949"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/categories?post=5949"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lode.uno\/linux-man\/wp-json\/wp\/v2\/tags?post=5949"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
SYNOPSIS<\/a>
DESCRIPTION<\/a>
EXAMPLES<\/a>
SEE ALSO<\/a>
KEYWORDS<\/a> <\/p>\n
\nNAME <\/a> <\/h2>\n
SYNOPSIS <\/a> <\/h2>\n
DESCRIPTION <\/a> <\/h2>\n
on<\/b> code variableList script<\/i><\/p>\nEXAMPLES <\/a> <\/h2>\n
try<\/b> {
puts $f “some message”
# …
} finally<\/b> {
close $f
}<\/p>\n
set f [open \/some\/file\/name w]
} trap<\/b> {POSIX EISDIR} {} {
puts “failed to open \/some\/file\/name: it\u2019s a directory”
} trap<\/b> {POSIX ENOENT} {} {
puts “failed to open \/some\/file\/name: it doesn\u2019t exist”
}<\/p>\nSEE ALSO <\/a> <\/h2>\n
KEYWORDS <\/a> <\/h2>\n
\n","protected":false},"excerpt":{"rendered":"