Perl/Code: Difference between revisions
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In a Linux/Unix environment it has become standard practise to include a special comment in a script's first line, which will direct the command interpreter (shell) where to find the executable, the so-called "hash bang" line. Usually the complete path to the executable is written, thus making this line in the script dependent on the host's file system structure. | In a Linux/Unix environment it has become standard practise to include a special comment in a script's first line, which will direct the command interpreter (shell) where to find the executable, the so-called "hash bang" line. Usually the complete path to the executable is written, thus making this line in the script dependent on the host's file system structure. | ||
Example: | Example: | ||
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This however requires that a valid Perl executable exists in <code>/usr/bin/</code> or the shell will produce an error. The '-w' option is always recommended, it will direct Perl to produce warnings about unsafe code such as using undeclared variables, and other potential traps. | This however requires that a valid Perl executable exists in <code>/usr/bin/</code> or the shell will produce an error. The '-w' option is always recommended, it will direct Perl to produce warnings about unsafe code such as using undeclared variables, and other potential traps. | ||
Latest revision as of 13:09, 24 March 2008
In a Linux/Unix environment it has become standard practise to include a special comment in a script's first line, which will direct the command interpreter (shell) where to find the executable, the so-called "hash bang" line. Usually the complete path to the executable is written, thus making this line in the script dependent on the host's file system structure.
Example:
#!/usr/bin/perl -w
# script 'tst'
print "Hello, world!\n";
Now, instead of running
$ perl tst
you can run just the script itself:
$ ./tst
which will produce the expected
Hello, world!
This however requires that a valid Perl executable exists in /usr/bin/ or the shell will produce an error. The '-w' option is always recommended, it will direct Perl to produce warnings about unsafe code such as using undeclared variables, and other potential traps.