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Full Discussion: Perl command line option '-n','-p' and multiple files: can it know a file name of a printed line?
Top Forums Shell Programming and Scripting Perl command line option '-n','-p' and multiple files: can it know a file name of a printed line? Post 302998343 by alex_5161 on Tuesday 30th of May 2017 02:48:48 PM
Old 05-30-2017
Perl command line option '-n','-p' and multiple files: can it know a file name of a printed line?
I am looking for help in processing of those options: '-n' or '-p'
I understand what they do and how to use them.
But, I would like to use them with more than one file (and without any shell-loop; loading the 'perl' once.)
I did try it and -n works on 2 files.
Question is:
- is it possible to distinguish from which file is a printed line?

So, I use command like:
Code:
perl -ne 'print " $.: $_" if /"\d\d"/' ./fl1 ./fl2

It have correctly selected lines, but I would like anyhow to get a file name where from each line is selected.
Not sure how to get it, if that is possible at all in such usage...

I understand the perl is using the
Code:
while (<>) {...}

I am not sure what is going to be read by the '<>'
- does it already concatenated the input files in shell before starting the Perl?
- Or Perl do it inside somehow?
Maybe it opening each file as standard-input, redirecting the stdin to a current file?!
If so, is it possible to get its name?

Will appreciate help, if you get some idea about how it works with more than one file!
(I understand, I could write everything without the '-n' or '-p', but would like to have that shortage be used,... if possible)
Thanks.
Last edited by rbatte1; 05-31-2017 at 06:45 AM..
 

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LEARN ABOUT LINUX

chsh

CHSH(1) 							   User Commands							   CHSH(1)

NAME

       chsh - change login shell

SYNOPSIS

       chsh [options] [LOGIN]

DESCRIPTION

       The chsh command changes the user login shell. This determines the name of the user's initial login command. A normal user may only change
       the login shell for her own account; the superuser may change the login shell for any account.

OPTIONS

       The options which apply to the chsh command are:

       -h, --help
	   Display help message and exit.

       -s, --shell SHELL
	   The name of the user's new login shell. Setting this field to blank causes the system to select the default login shell.

       If the -s option is not selected, chsh operates in an interactive fashion, prompting the user with the current login shell. Enter the new
       value to change the shell, or leave the line blank to use the current one. The current shell is displayed between a pair of [ ] marks.

NOTE

       The only restriction placed on the login shell is that the command name must be listed in /etc/shells, unless the invoker is the superuser,
       and then any value may be added. An account with a restricted login shell may not change her login shell. For this reason, placing /bin/rsh
       in /etc/shells is discouraged since accidentally changing to a restricted shell would prevent the user from ever changing her login shell
       back to its original value.

FILES

       /etc/passwd
	   User account information.

       /etc/shells
	   List of valid login shells.

       /etc/login.defs
	   Shadow password suite configuration.

SEE ALSO

       chfn(1), login.defs(5), passwd(5).

User Commands							    06/24/2011								   CHSH(1)
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