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How do I execute unix commands in perl script.? 3
- Thread starter vptl
- Start date
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2
- #2
TrojanWarBlade
Programmer
You can use either backticks ("`") or the "system()" function to call your shell commands in Perl
E.g.
or
But you might be better learning how to write perl code to do these tasks. Perl can read directories, read from pipelines, split your records up and pick out the fields as well as write output files if you need them.
You may, of course, find that once you write these things in perl that you no longer need to write so many temporary files.
In Unix, you can usually use "perldoc" to get access to the perl documentation.
Trojan
E.g.
Code:
`ls -l |awk '{print $4}' >> /tmp/o`;
Code:
system('ls -l |awk '{print $4}' >> /tmp/o');But you might be better learning how to write perl code to do these tasks. Perl can read directories, read from pipelines, split your records up and pick out the fields as well as write output files if you need them.
You may, of course, find that once you write these things in perl that you no longer need to write so many temporary files.
In Unix, you can usually use "perldoc" to get access to the perl documentation.
Trojan
- Thread starter
- #5
TrojanWarBlade
Programmer
LOL
Well spotted Dmazzini!
Ironic?!
Well spotted Dmazzini!
Ironic?!
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1
- #7
TrojanWarBlade
Programmer
vpti,
Somehow I doubt that the commands you run in your "system()" function will be platform independant.
Trojan
Somehow I doubt that the commands you run in your "system()" function will be platform independant.
Trojan
A very comment from TrojanWarBlade , may be vptl you could execute a command asking first for the operating system.....
($^O =~ /Win/ ) ? system("notepad.exe $file") : system( "/usr/dt/bin/dtpad -standAlone -noReadOnlyWarning -viewOnly $file \&" );
dmazzini
GSM System and Telecomm Consultant
, may be vptl you could execute a command asking first for the operating system.....($^O =~ /Win/ ) ? system("notepad.exe $file") : system( "/usr/dt/bin/dtpad -standAlone -noReadOnlyWarning -viewOnly $file \&" );
dmazzini
GSM System and Telecomm Consultant
TrojanWarBlade
Programmer
Pipelines are another way that have not yet really been discussed.
I use this as a dumb example only since I would never recommend using "ls" or "awk" in a pipeline but it demonstrates the principle.
Trojan
Code:
open PIPE, "ls -l |awk '{print \$4}' |" or die "failed to open pipe";
while(<PIPE>) {
chomp;
# Process each line here
}
close PIPE;I use this as a dumb example only since I would never recommend using "ls" or "awk" in a pipeline but it demonstrates the principle.
Trojan
- Thread starter
- #11
Thanks all for their input.
I am still not haveing luck...please see
this is my line 51 in my code.(Running on solaris)
I tried with and w/o backslash before ">" redirection.
system(`/nas/bin/nas_fs -list | egrep -v 'root|name' | awk '{print $6}'|sed '/^$/d' \> /tmp/fs_list`);
The error I get is
Use of uninitialized value in concatenation (.) at /tmp/b line 51, <STDIN> line 3.
sed: -e expression #1, char 2: Unterminated address regex
Please let me know what is not correct here...I can run this on my shell works fine.
I am still not haveing luck...please see
this is my line 51 in my code.(Running on solaris)
I tried with and w/o backslash before ">" redirection.
system(`/nas/bin/nas_fs -list | egrep -v 'root|name' | awk '{print $6}'|sed '/^$/d' \> /tmp/fs_list`);
The error I get is
Use of uninitialized value in concatenation (.) at /tmp/b line 51, <STDIN> line 3.
sed: -e expression #1, char 2: Unterminated address regex
Please let me know what is not correct here...I can run this on my shell works fine.
TrojanWarBlade
Programmer
You must not mix backticks with the "system()" function.
You are effectively executing the shell and then treating the result as another shell command to execute.
Also, you must be very careful of perl's metacharacters. They will all need to be escaped if used in backticks (or double quotes).
The "$" character will be causing you problems.
To fix, replace the backticks with double quotes and escape the "$" characters with a backslash ("\$") in all places.
Alternatively, you can create your own quotes in perl so here we could do something like this:
The q introduces the (single) quote character and I chose "!" for this example so a simple example string is:
(by way of explanation).
Since this is a user defined single quoted we do not have to worry about escaping metacharacters.
Trojan
You are effectively executing the shell and then treating the result as another shell command to execute.
Also, you must be very careful of perl's metacharacters. They will all need to be escaped if used in backticks (or double quotes).
The "$" character will be causing you problems.
To fix, replace the backticks with double quotes and escape the "$" characters with a backslash ("\$") in all places.
Alternatively, you can create your own quotes in perl so here we could do something like this:
Code:
system(q!/nas/bin/nas_fs -list | egrep -v 'root|name' | awk '{print $6}'|sed '/^$/d' > /tmp/fs_list!);The q introduces the (single) quote character and I chose "!" for this example so a simple example string is:
Code:
my $string = q!This is a string!;Since this is a user defined single quoted we do not have to worry about escaping metacharacters.
Trojan
- Thread starter
- #13
- Thread starter
- #16
Trojan's earlier point is well made - perl has facilities for doing many of the things you are shelling out to other programs to get. The difference being that (in most cases, anyway) that the perl functions are platform-independent. So if your script needs to be portable, try to use the perl functions where possible.
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