I wrote a collection of bash functions years ago and now need to use them again but
I'm getting some error messages when eval tries to expand the variables names.
The problem is ~ is not being expanded. It turns out to be a little tricky to expand ~ but also avoid word separation on the path name (white spaces in you array source filename).
Try:
These 2 Users Gave Thanks to Chubler_XL For This Post:
I have a little script to help me manage a gallery of image files. It makes symbolic links to every file in and below the current directory, placing them in a target directory which is passed to the script as a parameter. Unfortunately, the script pukes when I pass a parameter that contains... (4 Replies)
If have
var='$variable'
how can I expand $variable.
I have tried many thing like duble quotes/braces etc, but nothing worked.
I need the solution ASAP. (2 Replies)
Hi,
The following code finds the line containing fruits in test.txt and replaces instances of apple with banana.
ed -s test.txt <<< $'/fruits/s/apple/banana/g\nw'
What I want to do is put variables in the place of fruits, apple and banana.
I have tried replacing ' with " to get... (2 Replies)
Hi,
I need some direction with the following. The below code is semi-psuedo code which will hopefully make it easier to understand what I am trying to achieve:
for i in `echo ${testarray
}`
do
let c=c+1
eval "first$c=$i"
while... (4 Replies)
Hello,
so i'm making a script, using dynamic variables and trying to expand them. So far it hasn't worked out too well so it seems that I need some help from you, the elite.
Example:
#!/bin/sh
counter=0
until (($counter>5))
counter2=1
until (($counter2>6)); do
if ;... (5 Replies)
Hi Guys,
I have an issue with awk and variables. I have trawled the internet and forums but can't seem to get the exactt syntax I need.
I have tried using awk -v and all sorts of variations but I have hit a brick wall. I have spent a full day on this and am just going round in circles.
... (3 Replies)
My OS is Linux (kernel 4.08.something) and AIX (7100-04-01-1543), the used ksh versions are:
ksh88: Version M-11/16/88f (AIX)
ksh93: Version M 93t+ 2009-05-01 (AIX), Version M 93u (Linux)
When writing a parser for stanza files in ksh i encountered a rather strange behavior. Here is a... (4 Replies)
I pass an argument to bash as run. The first command in green executes as expected, however the second in blue fails as the $run does not expand. I tried to escape the variable with \ thinking the quotes were making the literal translation and also "${run}" but both did not work to expand the... (3 Replies)
Perl::Critic::Policy::ErrorHandling::RequireCheckingRetuUserlContributed PPerl::Critic::Policy::ErrorHandling::RequireCheckingReturnValueOfEval(3)NAME
Perl::Critic::Policy::ErrorHandling::RequireCheckingReturnValueOfEval - You can't depend upon the value of "$@"/"$EVAL_ERROR" to tell
whether an "eval" failed.
AFFILIATION
This Policy is part of the core Perl::Critic distribution.
DESCRIPTION
A common idiom in perl for dealing with possible errors is to use "eval" followed by a check of $@/$EVAL_ERROR:
eval {
...
};
if ($EVAL_ERROR) {
...
}
There's a problem with this: the value of $EVAL_ERROR can change between the end of the "eval" and the "if" statement. The issue is object
destructors:
package Foo;
...
sub DESTROY {
...
eval { ... };
...
}
package main;
eval {
my $foo = Foo->new();
...
};
if ($EVAL_ERROR) {
...
}
Assuming there are no other references to $foo created, when the "eval" block in "main" is exited, "Foo::DESTROY()" will be invoked,
regardless of whether the "eval" finished normally or not. If the "eval" in "main" fails, but the "eval" in "Foo::DESTROY()" succeeds,
then $EVAL_ERROR will be empty by the time that the "if" is executed. Additional issues arise if you depend upon the exact contents of
$EVAL_ERROR and both "eval"s fail, because the messages from both will be concatenated.
Even if there isn't an "eval" directly in the "DESTROY()" method code, it may invoke code that does use "eval" or otherwise affects
$EVAL_ERROR.
The solution is to ensure that, upon normal exit, an "eval" returns a true value and to test that value:
# Constructors are no problem.
my $object = eval { Class->new() };
# To cover the possiblity that an operation may correctly return a
# false value, end the block with "1":
if ( eval { something(); 1 } ) {
...
}
eval {
...
1;
}
or do {
# Error handling here
};
Unfortunately, you can't use the "defined" function to test the result; "eval" returns an empty string on failure.
Various modules have been written to take some of the pain out of properly localizing and checking $@/$EVAL_ERROR. For example:
use Try::Tiny;
try {
...
} catch {
# Error handling here;
# The exception is in $_/$ARG, not $@/$EVAL_ERROR.
}; # Note semicolon.
"But we don't use DESTROY() anywhere in our code!" you say. That may be the case, but do any of the third-party modules you use have them?
What about any you may use in the future or updated versions of the ones you already use?
CONFIGURATION
This Policy is not configurable except for the standard options.
SEE ALSO
See thread on perl5-porters starting here: <http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2008-06/msg00537.html>.
For a nice, easy, non-magical way of properly handling exceptions, see Try::Tiny.
AUTHOR
Elliot Shank "<perl@galumph.com>"
COPYRIGHT
Copyright (c) 2008-2011 Elliot Shank.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. The full text of this license
can be found in the LICENSE file included with this module.
perl v5.16.32014-0Perl::Critic::Policy::ErrorHandling::RequireCheckingReturnValueOfEval(3)