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Perl one liner executing a shell command on…

Perl one liner executing a shell command on files.

e.g. copy all *.c files to new names, *.R.

perl -de 'foreach (@ARGV) {($new = $_) =~ s/c$/R/; system("cp $_ $new");}' *c
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Diff sort output diff

Diff sort output.

diff <(sort file1) <(sort file2)
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Select random contents from a file Sort sort…

Select random contents from a file

Sort

sort -R infile | head -n 3000

Perl

perl -n -e 'print if (rand > 0.1)' infile
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Display file system status in Unix stat

Display file system status in Unix

stat
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Find files and show the content recursively in…

Find files and show the content recursively in unix.

find . -name "readme" -exec head {} \;
find . -name "readme" | xargs head
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Find duplicate or unique records in unix sort…

Find duplicate or unique records in unix

sort is essential because uniq find successive identical lines.
Unique records

cat data.txt | sort | uniq

Duplicate records

cat data.txt | sort | uniq -d
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Display file contents with file names tail +1…

Display file contents with file names;

tail +1 many_files*

It works on Mac, BSD.

For GNU tail, use

tail -n +1 many_files*

Update: GNU tail has different parameters.

http://stackoverflow.com/questions/5917413/cat-multiple-files-but-include-filename-as-headers

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Defining Macros on the Command Line Macros can…

Defining Macros on the Command Line

Macros can be defined on the Make command line. For example:

make CFLAGS=–ms
would start up Make and define the macro CFLAGS with the value “–ms”. Macros defined on the command line take precedence over macros of the same name defined in the makefile.

If a command-line macro contains spaces, it must be enclosed in double quotes as in:

make “CFLAGS=-ms -z -p”

http://www.opussoftware.com/tutorial/TutMakefile.htm

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Rename multiple files on Linux If you are…

Rename multiple files on Linux
If you are lucky to have rename installed on your system, use it.
Rename is a Perl program and can take Perl regular expression.

rename 's/^comp/compare/' *pdf

Or copy the code below.

http://www.perlmonks.org/?node_id=632437


#!/usr/bin/perl -w
#
#  This script was developed by Robin Barker (Robin.Barker@npl.co.uk),
#  from Larry Wall's original script eg/rename from the perl source.
#
#  This script is free software; you can redistribute it and/or modify it
#  under the same terms as Perl itself.
#
# Larry(?)'s RCS header:
#  RCSfile: rename,v   Revision: 4.1   Date: 92/08/07 17:20:30 
#
# $RCSfile: rename,v $$Revision: 1.5 $$Date: 1998/12/18 16:16:31 $
#
# $Log: rename,v $
# Revision 1.5  1998/12/18 16:16:31  rmb1
# moved to perl/source
# changed man documentation to POD
#
# Revision 1.4  1997/02/27  17:19:26  rmb1
# corrected usage string
#
# Revision 1.3  1997/02/27  16:39:07  rmb1
# added -v
#
# Revision 1.2  1997/02/27  16:15:40  rmb1
# *** empty log message ***
#
# Revision 1.1  1997/02/27  15:48:51  rmb1
# Initial revision
#

use strict;

use Getopt::Long;
Getopt::Long::Configure('bundling');

my ($verbose, $no_act, $force, $op);

die "Usage: rename [-v] [-n] [-f] perlexpr [filenames]\n"
    unless GetOptions(
	'v|verbose' => \$verbose,
	'n|no-act'  => \$no_act,
	'f|force'   => \$force,
    ) and $op = shift;

$verbose++ if $no_act;

if (!@ARGV) {
    print "reading filenames from STDIN\n" if $verbose;
    @ARGV = <STDIN>;
    chop(@ARGV);
}

for (@ARGV) {
    my $was = $_;
    eval $op;
    die $@ if $@;
    next if $was eq $_; # ignore quietly
    if (-e $_ and !$force)
    {
	warn  "$was not renamed: $_ already exists\n";
    }
    elsif ($no_act or rename $was, $_)
    {
	print "$was renamed as $_\n" if $verbose;
    }
    else
    {
	warn  "Can't rename $was $_: $!\n";
    }
}

__END__

=head1 NAME

rename - renames multiple files

=head1 SYNOPSIS

B<rename> S<[ B<-v> ]> S<[ B<-n> ]> S<[ B<-f> ]> I<perlexpr> S<[ I<files> ]>

=head1 DESCRIPTION

C<rename>
renames the filenames supplied according to the rule specified as the
first argument.
The I<perlexpr> 
argument is a Perl expression which is expected to modify the C<$_>
string in Perl for at least some of the filenames specified.
If a given filename is not modified by the expression, it will not be
renamed.
If no filenames are given on the command line, filenames will be read
via standard input.

For example, to rename all files matching C<*.bak> to strip the extension,
you might say

	rename 's/\.bak$//' *.bak

To translate uppercase names to lower, you'd use

	rename 'y/A-Z/a-z/' *

=head1 OPTIONS

=over 8

=item B<-v>, B<--verbose>

Verbose: print names of files successfully renamed.

=item B<-n>, B<--no-act>

No Action: show what files would have been renamed.

=item B<-f>, B<--force>

Force: overwrite existing files.

=back

=head1 ENVIRONMENT

No environment variables are used.

=head1 AUTHOR

Larry Wall

=head1 SEE ALSO

mv(1), perl(1)

=head1 DIAGNOSTICS

If you give an invalid Perl expression you'll get a syntax error.

=head1 BUGS

The original C<rename> did not check for the existence of target filenames,
so had to be used with care.  I hope I've fixed that (Robin Barker).

=cut

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Sort files according to the creation time on…

Sort files according to the creation time on Unix

Sort by the last saved time

ls -ltr

Sort by the created time

ls -lUr