I am looking for a Perl oneliner (inserting it into Bash script), and I need the next interface:
perl -0777 -nlE 'commands' file1 file2 .... fileN
I created the next:
perl -0777 -lnE 'BEGIN{$str=quotemeta(do{local(#ARGV, $/)="file1"; <>})} say "working on $ARGV" if $_ =~ /./' "$#"
Prettier:
perl -0777 -lnE '
BEGIN{
$str = quotemeta(
do{
local(#ARGV, $/)="file1"; <> #localize ARGV to "file1.txt" for <>
}
)
}
say "working on $ARGV" if $_ =~ /./ #demo only action
' "$#"
It works, but with this I need edit the source code every time when needing to change file1.
How do I change the script to the following?
Slurp the $ARGV[0] (file1) into $str (in the BEGIN block)
And slurp the other arguments into $_ in the main loop
Pass it as an argument, removing it from #ARGV in the BEGIN block.
$ echo foo >refile
$ echo -ne 'foo\nbar\nfood\nbaz\n' >file1
$ echo -ne 'foo\nbar\nfood\nbaz\n' >file2
$ perl -lnE'
BEGIN {
local #ARGV = shift(#ARGV);
$re = join "|", map quotemeta, <>;
}
say "$ARGV:$.:$_" if /$re/;
close(ARGV) if eof; # Reset $.
' refile file1 file2
file1:1:foo
file1:3:food
file2:1:foo
file2:3:food
Related
Can anyone explain the difference in output of the two perl (using cygwin) commands below:
$ echo abc | perl -n -e 'if ($_ =~ /a/) {print 1;}'
prints :
1
$ echo abc | perl -e 'if ($_ =~ /a/) {print 1;}'
The first prints '1' while second one outputs blank?
Thanks
-n switch adds while loop around your code, so in your case $_ is populated from standard input. In second example there is no while loop thus $_ is leaved undefined.
Using Deparse you can ask perl to show how your code is parsed,
perl -MO=Deparse -n -e 'if ($_ =~ /a/) {print 1;}'
LINE: while (defined($_ = <ARGV>)) {
if ($_ =~ /a/) {
print 1;
}
}
perl -MO=Deparse -e 'if ($_ =~ /a/) {print 1;}'
if ($_ =~ /a/) {
print 1;
}
I am understanding perl in command line, please help me
what is equivalent in perl
awk '{for(i=1;i<=NF;i++)printf i < NF ? $i OFS : $i RS}' file
awk '!x[$0]++' file
awk 'FNR==NR{A[$0];next}($0 in A)' file1 file2
awk 'FNR==NR{A[$1]=$5 OFS $6;next}($1 in A){print $0,A[$1];delete A[$1]}' file1 file1
Please someone help me...
Try the awk to perl translator. For example:
$ echo awk '!x[$0]++' file | a2p
#!/usr/bin/perl
eval 'exec /usr/bin/perl -S $0 ${1+"$#"}'
if $running_under_some_shell;
# this emulates #! processing on NIH machines.
# (remove #! line above if indigestible)
eval '$'.$1.'$2;' while $ARGV[0] =~ /^([A-Za-z_0-9]+=)(.*)/ && shift;
# process any FOO=bar switches
while (<>) {
chomp; # strip record separator
print $_ if $awk;print $_ if !($X{$_}++ . $file);
}
You can ignore the boiler plate at the beginning and see the meat of the perl in the while loop. The translation is seldom perfect (even in this simple example, the perl code omits newlines), but it usually provides a reasonable approximation.
Another example (the one Peter is having trouble with in the comments):
$ echo '{for(i=1;i<=NF;i++)printf( i < NF ? ( $i OFS ) : ($i RS))}' | a2p
#!/usr/bin/perl
eval 'exec /usr/bin/perl -S $0 ${1+"$#"}'
if $running_under_some_shell;
# this emulates #! processing on NIH machines.
# (remove #! line above if indigestible)
eval '$'.$1.'$2;' while $ARGV[0] =~ /^([A-Za-z_0-9]+=)(.*)/ && shift;
# process any FOO=bar switches
$, = ' '; # set output field separator
while (<>) {
chomp; # strip record separator
#Fld = split(' ', $_, -1);
for ($i = 1; $i <= ($#Fld+1); $i++) {
printf (($i < ($#Fld+1) ? ($Fld[$i] . $,) : ($Fld[$i] . $/)));
}
}
Is there a simple way to mimic the effect of the -l command-line switch within perl scripts? (Of course, I can always chomp each line and then append "\n" to each line I print, but the point is to avoid having to do this.)
No. You can get the automatic appending of "\n" by using $\, but you have to add the chomp yourself.
Here's how -l works.
$ perl -MO=Deparse -ne 'print $_'
LINE: while (defined($_ = <ARGV>)) {
print $_;
}
$ perl -MO=Deparse -lne 'print $_'
BEGIN { $/ = "\n"; $\ = "\n"; } # -l added this line
LINE: while (defined($_ = <ARGV>)) {
chomp $_; # -l added this line
print $_;
}
(The comments are mine.) Notice that -l added a literal chomp $_ at the beginning of the loop generated by -n (and it only does that if you use -n or -p). There's no variable you can set to mimic that behaviour.
It's a little-known fact that -l, -n, and -p work by wrapping boilerplate text around the code you supply before it's compiled.
Yes, try using this at the beginning of your script after the shebang and strictures:
$/ = $\ = "\n"; # setting the output/input record separator like OFS in awk
and use in the loop :
chomp;
print;
Or like this :
use strict; use warnings;
use English qw/-no_match_vars/;
$OUTPUT_RECORD_SEPARATOR = "\n";
while (<>) {
chomp;
print;
}
I do not recommend to use
#!/usr/bin/perl -l
for a better clarity =)
See perldoc perlvar
You can add it to your shebang line:
#!/usr/bin/perl -l
How can I write a Perl script to convert a text file to all upper case letters?
perl -ne "print uc" < input.txt
The -n wraps your command line script (which is supplied by -e) in a while loop. A uc returns the ALL-UPPERCASE version of the default variable $_, and what print does, well, you know it yourself. ;-)
The -p is just like -n, but it does a print in addition. Again, acting on the default variable $_.
To store that in a script file:
#!perl -n
print uc;
Call it like this:
perl uc.pl < in.txt > out.txt
$ perl -pe '$_= uc($_)' input.txt > output.txt
perl -pe '$_ = uc($_)' input.txt > output.txt
But then you don't even need Perl if you're using Linux (or *nix). Some other ways are:
awk:
awk '{ print toupper($0) }' input.txt >output.txt
tr:
tr '[:lower:]' '[:upper:]' < input.txt > output.txt
$ perl -Tpe " $_ = uc; " --
$ perl -MO=Deparse -Tpe " $_ = uc; " -- a s d f
LINE: while (defined($_ = <ARGV>)) {
$_ = uc $_;
}
continue {
die "-p destination: $!\n" unless print $_;
}
-e syntax OK
$ cat myprogram.pl
#!/usr/bin/perl -T --
LINE: while (defined($_ = <ARGV>)) {
$_ = uc $_;
}
continue {
die "-p destination: $!\n" unless print $_;
}
How could I convert:
awk '{print $2 >> $1}' file
in a short Perl one-liner?
"file" could look like this:
fruit banana
vegetable beetroot
vegetable carrot
mushroom chanterelle
fruit apple
there may some other ways, but here's what i can think of
perl -ane 'open(FILE,">>",$F[0]); print FILE $F[1];close(FILE);' file
I guess awk has to be better at some things :-)
This is right at the limit of what I'd do on the command line, but it avoids reopening filehandles.
$ perl -lane '$fh{$F[0]} || open $fh{$F[0]}, ">>", $F[0]; print {$fh{$F[0]}} $F[1]' file
Not pure Perl, but you can do:
perl -nae '`echo $F[1] >> $F[0]`' input_file
This is what a2p <<< '{print $2 >> $1}' produces
#!/usr/bin/perl
eval 'exec /usr/bin/perl -S $0 ${1+"$#"}'
if $running_under_some_shell;
# this emulates #! processing on NIH machines.
# (remove #! line above if indigestible)
eval '$'.$1.'$2;' while $ARGV[0] =~ /^([A-Za-z_0-9]+=)(.*)/ && shift;
# process any FOO=bar switches
$, = ' '; # set output field separator
$\ = "\n"; # set output record separator
while (<>) {
($Fld1,$Fld2) = split(' ', $_, -1);
&Pick('>>', $Fld1) &&
(print $fh $Fld2);
}
sub Pick {
local($mode,$name,$pipe) = #_;
$fh = $name;
open($name,$mode.$name.$pipe) unless $opened{$name}++;
}