Difference between revisions of "Perl"
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m (→Warning) |
m (→Warning) |
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Line 43: | Line 43: | ||
==Warning== | ==Warning== | ||
− | If testing for existence of a hash key beware that all intermediate keys will be | + | If testing for existence of a hash key beware that all intermediate keys will be created by the test. In below example $hash1($key} will be created if it does not exist yet. |
<syntaxhighlight lang=Perl> | <syntaxhighlight lang=Perl> | ||
if (exists $hash1{$key1}{$key2) { | if (exists $hash1{$key1}{$key2) { |
Revision as of 13:14, 17 December 2018
Things that do work
Searching and matching is explained in Regular Expressions.
Print out the contents of $variable in a structured format.
use Data::Dumper;
print Dumper($variable);
if-then-else:
if < expr > {
<codeblock>
} elsif < expr ) {
<codeblock>
} else {
<codeblock>
}
print Dumper($variable);
- $var += <value>
- Add <value> to $var (works for -, *, / too)
- $string .= $addstring
- Concatenate $string and $addstring
- $string =~ s/<regexp>/<newvalue>/[g]
- Substitute <regexp> with <newvalue> in $string. The g modifier makes the all occurrences of <regexp> are substituted.
- $newstring = substr($string,start,length)
- Return substring of $string
- sprintf(format,$string)
- Return formatted string. format is e.g. "%.3f". Check Python:Strings#Advanced for all formats.
- $exitcode = system("a command")
- Executed the command in a subprocess and return the exitcode
- $output = `a command`
- Execute the command and return all command output
Warning
If testing for existence of a hash key beware that all intermediate keys will be created by the test. In below example $hash1($key} will be created if it does not exist yet.
if (exists $hash1{$key1}{$key2) {
...
} else {
...
}