Difference between revisions of "Perl"
Jump to navigation
Jump to search
Line 41: | Line 41: | ||
;$output = `a command` | ;$output = `a command` | ||
:Execute the command and return all command output | :Execute the command and return all command output | ||
+ | |||
+ | ==Warning== | ||
+ | If testing for existence of a hash key beware that all intermediate keys will be create by the test | ||
+ | In below example $hash1($key} will be created if it does not exist yet. | ||
+ | <syntaxhighlight lang=Perl> | ||
+ | if (exists $hash1{$key1}{$key2) { | ||
+ | ... | ||
+ | } else { | ||
+ | ... | ||
+ | } | ||
+ | </syntaxhighlight> |
Revision as of 16:32, 14 August 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 create by the test In below example $hash1($key} will be created if it does not exist yet.
if (exists $hash1{$key1}{$key2) {
...
} else {
...
}