Hi:
perl -e 'print "hello world!\n"'
A simple filter:
perl -ne 'print if /REGEX/'
Filter out blank lines (in place):
perl -i -ne'print if /\w/'
Search and replace (in place):
perl -i -pe's/SEARCH/REPLACE/'
Add first and penultimate columns:
perl -lane 'print $F[0] + $F[-2]'
Just lines 15 to 17:
perl -ne 'print if 15 .. 17' *.pod
In-place edit of *.c files changing all foo to bar:
perl -p -i.bak -e 's/\bfoo\b/bar/g' *.c
Command-line that prints the first 50 lines (cheaply):
perl -pe 'exit if $. > 50' f1 f2 f3 ...
Delete first 10 lines:
perl -i.old -ne 'print unless 1 .. 10' foo.txt
Change all the isolated oldvar occurrences to newvar:
perl -i.old -pe 's{\boldvar\b}{newvar}g' *.[chy]
Command-line that reverses the whole file by lines:
perl -e 'print reverse <>' file1 file2 file3 ....
Find palindromes:
perl -lne 'print if $_ eq reverse' /usr/dict/words
Command-line that reverse all the bytes in a file:
perl -0777e 'print scalar reverse <>' f1 f2 f3 ...
Command-line that reverses the whole file by paragraphs:
perl -00 -e 'print reverse <>' file1 file2 file3 ....
Increment all numbers found in these files:
perl i.tiny -pe 's/(\d+)/ 1 + $1 /ge' file1 file2 ....
Command-line that shows each line with its characters backwards:
perl -nle 'print scalar reverse $_' file1 file2 file3 ....
Delete all but lines between START and END:
perl -i.old -ne 'print unless /^START$/ .. /^END$/' foo.txt
Binary edit (careful!):
perl -i.bak -pe 's/Mozilla/Slopoke/g' /usr/local/bin/netscape
Duplicate words:
perl -0777 -ne 'print "$.: doubled $_\n" while /\b(\w+)\b\s+\b\1\b/gi'
Print the last 50 lines (expensive!):
perl -e '@lines = <>; print @lines[ $#lines .. $#lines-50' f1 f2 f3 ...
Move files < 1000 bytes to DIR:
ls -l *xls | perl -na -F'/\s+/' -e 'print "$F[8]\n" if $F[4] < 1000' |
xargs -J % mv % DIR
Print 1st, 2nd, and last columns (use -l for auto-line-end processing):
perl -F"\t" -nlae'print join "\t", @F[0,1,-1]'
Print columns 1-20:
perl -F"\t" -nlae'print join "\t", @F[0..19]'
Print all filenames & their line #s w/ pattern:
perl -ne'if (/PATTERN/) { print "$ARGV: $.\n" }; $. = 0 if eof'
Print file up to some pattern:
perl -ne'if (/PATTERN/) { close ARGV } else { print }'
Inclusive of line w/ pattern:
perl -pe'if (/PATTERN/) { close ARGV }'
Delete columns of file after column N+2:
perl -i -F'\t' -nlae'print join "\t", @F[0..N]'
Insert new column after column N:
perl -i -F'\t' -nae'print join "\t", @F[0..N], "new", @F[N+1..$#F]'
Cut files in dir at pattern & omit blank lines:
perl -i -ne 'if (/PATTERN/) { close ARGV } else { print unless /^$/ }'
Insert line numbers in a file:
perl -i -ne 'printf "%04d %s", $., $_'
Insert text at line N:
perl -i -pe 'print "text\n" if $. == N; $. = 0 if eof'
Print filenames of files containing pattern in first N lines:
perl -n -e 'if (/PATTERN/) { print "$ARGV\n"; close ARGV }'
-e 'close $ARGV if $. = N'
Return part of select filenames:
perl -ne '$ARGV =~ /^(.*)\.TXT$/; print "$&\n"; close ARGV'
Add columns M thru N and insert total:
perl -F'\t' -nlae '$t=0; $t += $_ for @F[M..N]; print "$_\t$t" '
Replace pattern on first line of each file:
perl -i -pe'
$new = 1;
s/PATTERN/REPLACE/ if $new;
$new = eof(ARGV) ? 1 : 0'
Create two columns of random numbers:
jot -r 100 | rs 50
Given a list of random numbers, ranging from 1 to 20, show the count of those numbers >= 10 and those < 10:
jot -r 20 1 20 | perl -ne 'print $_ >= 10 ? 1 : 0, "\n"' | sort | uniq -c
... or showing percentages:
jot -r 20 1 20
| perl -ne 'print $_ >= 10 ? 1 : 0, "\n"'
| sort
| uniq -c
| cut -c 3-4
| perl -ne'chomp; $sum += $_; push @counts, $_;
END { print $_, " : ", $_ / $sum, "\n" for @counts }'
... or to show the percentage of nines in the list:
| perl -ne 'print $_ == 9 ? 1 : 0, "\n"'
Given a list of numbers, ranging from 0 to 20,000, show the distribtion (i.e., individual counts) of those numbers after each is rounded to the nearest $1,000 increment:
jot -r 20 0 20000
| perl -pe'$_ = 1000 * int($_/1000)."\n"'
| sort -n
| uniq -c
... or showing percentages:
jot -r 20 1000 20000
| perl -pe'$_ = 1000 * int($_/1000) . "\n"'
| sort -n
| uniq -c
| perl -ne'($n,$num) = /(\d+)/g; $counts{$num} = $n; $sum += $n;
END { print $_,
" : ",
$counts{$_} / $sum, "\n"
for sort {$a<=>$b} keys %counts }'
... or to find the median (i.e., the middle number):
| perl -e'@lines = <>; print $lines[int($#lines/2)]'
... or to find the average:
jot -r 20 0 20000 | perl -pe'$_=1000 * int($_/1000)."\n"'