I am new to Perl and currently I am passing the command line arguments to a perl script and retrieving it via ARGS[0].
perl <perlscript.pl> windows IE.
I would like to give keywords to the values mentioned above.
perl <perlscript.pl> -os windows -browser IE -instance 2.
There might be times where instance might or might not be present. How do I go about handling this in my perl script.
Use Getopt::Long and store your options in a hash:
use warnings;
use strict;
use Getopt::Long qw(GetOptions);
my %opt;
GetOptions(\%opt, qw(
os=s
browser=s
instance=i
)) or die;
There are several modules for handling command line arguments: Getopt::Declare and Getopt::Long are probably the most popular. At my work we mainly use Getopt::Declare so Ill show and example of that since #toolic covered Getopt::Long.
my $ARGS = Getopt::Declare->new(
join("\n",
"[strict]",
"-os <string> The operating system [required]",
"-browser <string> The web browser [required]",
"-instance <int> The instance"
)
) or die;
Now you can access any of the parmeters via the $ARGS hash. i.e. $ARGS->{-os}
[strict] parses the command line strictly and reports any errors.
[required] after an option declaration means that field must be there, note I left it off of instance.
Related
What would be an example of how I can call a shell command, say 'ls -a' in a Perl script and the way to retrieve the output of the command as well?
How to run a shell script from a Perl program
1. Using system system($command, #arguments);
For example:
system("sh", "script.sh", "--help" );
system("sh script.sh --help");
System will execute the $command with
#arguments and return to your script when finished. You may check $!
for certain errors passed to the OS by the external application. Read
the documentation for system for the nuances of how various
invocations are slightly different.
2. Using exec
This is very similar to the use of system, but it will
terminate your script upon execution. Again, read the documentation
for exec for more.
3. Using backticks or qx//
my $output = `script.sh --option`;
my $output = qx/script.sh --option/;
The backtick operator and it's equivalent qx//, excute the command and options inside the operator and return that commands output to STDOUT when it finishes.
There are also ways to run external applications through creative use of open, but this is advanced use; read the documentation for more.
From Perl HowTo, the most common ways to execute external commands from Perl are:
my $files = `ls -la` — captures the output of the command in $files
system "touch ~/foo" — if you don't want to capture the command's output
exec "vim ~/foo" — if you don't want to return to the script after executing the command
open(my $file, '|-', "grep foo"); print $file "foo\nbar" — if you want to pipe input into the command
Examples
`ls -l`;
system("ls -l");
exec("ls -l");
Look at the open function in Perl - especially the variants using a '|' (pipe) in the arguments. Done correctly, you'll get a file handle that you can use to read the output of the command. The back tick operators also do this.
You might also want to review whether Perl has access to the C functions that the command itself uses. For example, for ls -a, you could use the opendir function, and then read the file names with the readdir function, and finally close the directory with (surprise) the closedir function. This has a number of benefits - precision probably being more important than speed. Using these functions, you can get the correct data even if the file names contain odd characters like newline.
As you become more experienced with using Perl, you'll find that there are fewer and fewer occasions when you need to run shell commands. For example, one way to get a list of files is to use Perl's built-in glob function. If you want the list in sorted order you could combine it with the built-in sort function. If you want details about each file, you can use the stat function. Here's an example:
#!/usr/bin/perl
use strict;
use warnings;
foreach my $file ( sort glob('/home/grant/*') ) {
my($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,$atime,$mtime,$ctime,$blksize,$blocks)
= stat($file);
printf("%-40s %8u bytes\n", $file, $size);
}
There are a lot of ways you can call a shell command from a Perl script, such as:
back tick
ls which captures the output and gives back to you.
system
system('ls');
open
Refer #17 here: Perl programming tips
You might want to look into open2 and open3 in case you need bidirectional communication.
I have been using system and qq to run linux programs inside perl. And it has worked well.
#!/usr/bin/perl # A hashbang line in perl
use strict; # It can save you a lot of time and headache
use warnings; # It helps you find typing mistakes
# my keyword in Perl declares the listed variable
my $adduser = '/usr/sbin/adduser';
my $edquota = '/usr/sbin/edquota';
my $chage = '/usr/bin/chage';
my $quota = '/usr/bin/quota';
my $nomeinteiro;
my $username;
my $home;
# system() function executes a system shell command
# qq() can be used in place of double quotes
system qq($adduser --home $home --gecos "$fullname" $username);
system qq($edquota -p john $username);
system qq($chage -E \$(date -d +180days +%Y-%m-%d) $username);
system qq($chage -l $username);
system qq($quota -s $username);
I want to extract user name, executing a perl script, within a script itself.
I am executing whoami linux command from perl as follows and it works pretty well.
my $whoami = `whoami`;
chomp $whoami;
print $whoami;
My intention is to get away from calling system commands from perl script. Therefore I am looking for Perl only solution. I was wondering if there is any CPAN module available which can extract system information.
Your suggestions in this regards will be appreciated.
perl -le 'print scalar getpwuid $<'
Perl have direct mapping to system getpw* functions.
These routines are the same as their counterparts in the system C
library. In list context, the return values from the various get
routines are as follows:
($name,$passwd,$uid,$gid,
$quota,$comment,$gcos,$dir,$shell,$expire) = getpw*
-- from perldoc -f getpwuid.
Use getpwuid with $< as argument (which, according to perldoc perlvar is "The real uid of this process", and also available as $REAL_USER_ID and $UID) and get first returned value.
You should probably take at look at the hash %ENV. It contains useful information about the environment where your script is run.
One example (in windows) to get the username would be:
perl -E "say $ENV{'USERNAME'}"
For bash substitute USERNAME for either LOGNAME or USER.
#!/usr/bin/perl -sw
use strict;
use warnings;
use Getopt::Long;
my $remote = 0;
my $test = 0;
GetOptions ('remote' => \$remote, 'test' => \$test);
print "$remote:$test\n";
perl test.pl --remote --test
The above prints "0:0". I am new to Perl so I have been unable to determine why this isn't working.
I also ran the "Simple Options" section from http://perldoc.perl.org/Getopt/Long.html#Simple-options and that didn't produce anything either.
I believe the -s command line option you include on your she-bang line is biting you. According to the perlrun documentation, the -s command line option:
enables rudimentary switch parsing for switches on the command line after the program name but before any filename arguments (or before an argument of --).
If you remove that option, things should work as you expect. I would also recommend removing the -w since you are already using the use warnings directive (the use warnings directive is much more fully featured, essentially replacing the -w option).
So, long story short, make your first line:
#!/usr/bin/perl
Note that if running the script on Windows via cmd you must specify perl before the script name otherwise GetOptions doesn't work.
When I tried simply calling my script.pl on the command line without first putting perl the script ran but all the options weren't parsed.
Trying to run this little perl program from parsCit:
parsCit-client.pl e1.txt
Too late for -CSD option at [filename] line 1
e1.txt is here: http://dl.dropbox.com/u/10557283/parserProj/e1.txt
I'm running the program from win7 cmd, not Cygwin.
filename is parsCit-client.pl - entire program is here:
#!/usr/bin/perl -CSD
#
# Simple SOAP client for the ParsCit web service.
#
# Isaac Councill, 07/24/07
#
use strict;
use encoding 'utf8';
use utf8;
use SOAP::Lite +trace=>'debug';
use MIME::Base64;
use FindBin;
my $textFile = $ARGV[0];
my $repositoryID = $ARGV[1];
if (!defined $textFile || !defined $repositoryID) {
print "Usage: $0 textFile repositoryID\n".
"Specify \"LOCAL\" as repository if using local file system.\n";
exit;
}
my $wsdl = "$FindBin::Bin/../wsdl/ParsCit.wsdl";
my $parsCitService = SOAP::Lite
->service("file:$wsdl")
->on_fault(
sub {
my($soap, $res) = #_;
die ref $res ? $res->faultstring :
$soap->transport->status;
});
my ($citations, $citeFile, $bodyFile) =
$parsCitService->extractCitations($textFile, $repositoryID);
#print "$citations\n";
#print "CITEFILE: $citeFile\n";
#print "BODYFILE: $bodyFile\n";
From perldoc perlrun, about the -C switch:
Note: Since perl 5.10.1, if the -C option is used on the "#!" line, it
must be specified on the command line as well, since the standard
streams are already set up at this point in the execution of the perl
interpreter. You can also use binmode() to set the encoding of an I/O
stream.
Which is presumably what the compiler means by it being "too late".
In other words:
perl -CSD parsCit-client.pl
Because command-line options in a #! "shebang" are not passed consistently across all operating systems (see this answer), and Perl has already opened streams before parsing the script shebang, and so cannot compensate for this in some older OSs, it was decided in bug 34087 to forbid -C in the shebang. Of course, not everyone was happy with this "fix", particularly if it would have otherwise worked on their OS and they don't want to think about anything other than UTF-8.
If you think binmode() is ugly and unnecessary (and doesn't cover command-line arguments), you might like to consider the utf8::all package which has a similar effect to perl -CSDL.
Or were you using *nix, I would suggest export PERL_UNICODE="SDA" in the enclosing script to get Perl to realise it's in a UTF-8 environment.
What would be an example of how I can call a shell command, say 'ls -a' in a Perl script and the way to retrieve the output of the command as well?
How to run a shell script from a Perl program
1. Using system system($command, #arguments);
For example:
system("sh", "script.sh", "--help" );
system("sh script.sh --help");
System will execute the $command with
#arguments and return to your script when finished. You may check $!
for certain errors passed to the OS by the external application. Read
the documentation for system for the nuances of how various
invocations are slightly different.
2. Using exec
This is very similar to the use of system, but it will
terminate your script upon execution. Again, read the documentation
for exec for more.
3. Using backticks or qx//
my $output = `script.sh --option`;
my $output = qx/script.sh --option/;
The backtick operator and it's equivalent qx//, excute the command and options inside the operator and return that commands output to STDOUT when it finishes.
There are also ways to run external applications through creative use of open, but this is advanced use; read the documentation for more.
From Perl HowTo, the most common ways to execute external commands from Perl are:
my $files = `ls -la` — captures the output of the command in $files
system "touch ~/foo" — if you don't want to capture the command's output
exec "vim ~/foo" — if you don't want to return to the script after executing the command
open(my $file, '|-', "grep foo"); print $file "foo\nbar" — if you want to pipe input into the command
Examples
`ls -l`;
system("ls -l");
exec("ls -l");
Look at the open function in Perl - especially the variants using a '|' (pipe) in the arguments. Done correctly, you'll get a file handle that you can use to read the output of the command. The back tick operators also do this.
You might also want to review whether Perl has access to the C functions that the command itself uses. For example, for ls -a, you could use the opendir function, and then read the file names with the readdir function, and finally close the directory with (surprise) the closedir function. This has a number of benefits - precision probably being more important than speed. Using these functions, you can get the correct data even if the file names contain odd characters like newline.
As you become more experienced with using Perl, you'll find that there are fewer and fewer occasions when you need to run shell commands. For example, one way to get a list of files is to use Perl's built-in glob function. If you want the list in sorted order you could combine it with the built-in sort function. If you want details about each file, you can use the stat function. Here's an example:
#!/usr/bin/perl
use strict;
use warnings;
foreach my $file ( sort glob('/home/grant/*') ) {
my($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,$atime,$mtime,$ctime,$blksize,$blocks)
= stat($file);
printf("%-40s %8u bytes\n", $file, $size);
}
There are a lot of ways you can call a shell command from a Perl script, such as:
back tick
ls which captures the output and gives back to you.
system
system('ls');
open
Refer #17 here: Perl programming tips
You might want to look into open2 and open3 in case you need bidirectional communication.
I have been using system and qq to run linux programs inside perl. And it has worked well.
#!/usr/bin/perl # A hashbang line in perl
use strict; # It can save you a lot of time and headache
use warnings; # It helps you find typing mistakes
# my keyword in Perl declares the listed variable
my $adduser = '/usr/sbin/adduser';
my $edquota = '/usr/sbin/edquota';
my $chage = '/usr/bin/chage';
my $quota = '/usr/bin/quota';
my $nomeinteiro;
my $username;
my $home;
# system() function executes a system shell command
# qq() can be used in place of double quotes
system qq($adduser --home $home --gecos "$fullname" $username);
system qq($edquota -p john $username);
system qq($chage -E \$(date -d +180days +%Y-%m-%d) $username);
system qq($chage -l $username);
system qq($quota -s $username);