Perl Oneliner Program

A Perl Oneliner Program is a CLI-based Perl program that can be expressed in one line of code.

• Context:
  • It can use Perl Interpreter Parameters.
• Example(s):
  • perl -ne 'chomp;@w=split(/\t/);print "$w[0]\t$w[2]\n"' file.tsv
• Counter-Example(s):
  • a Python Oneliner Program.
  • an AWK Program.
• See: Perl Coding Example, Perl Program Template.

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Notes

coding examples of Perl Oneliner Program

wrap each line with <s> … </s>

% perl -ne 'print “<s>$_<\/s>"' file.txt

print the first and third column of a tab separated file

% perl -ne 'chomp;@w=split(/\t/);print "$w[0]\t$w[2]\n"' file.tsv

print the text that follows "artid=" but before a "&"

perl -ne 's/.*?artid=(.*?)[&"].*/$1/;print "$_\n" file.txt

cut out content that matches a pattern (within < xxx >)

perl -ne 'chomp;s/<\d.+?jpg.+?>g; print "$_\n"' file.txt

update file contents in place

simple pattern

perl -pi -e 's/you/me/g' file

a path string within the files under the local directory

% perl -i.bak -p -e "s#/home/george#/home/curious#" `find . -print`

repeated strings

finding all repeated lines in a file?

perl -ne 'print if $a{$_}++' file

report the count of each repeated string

perl -ne 'while (<>) {chomp; $hash{lc($_)}++};       @sorted = sort { $hash{$a} < $hash{$b} } keys %hash ; foreach (@sorted) {print "$hash{$_} $_\n"}'
perl -ne 'chomp;split;foreach (@_){$hash{lc($_)}++}; @sorted = sort { $hash{$a} < $hash{$b} } keys %hash ; foreach (@sorted) {print "$hash{$_} $_\n"}'

use a package

use package to sum the numbers in a file

perl -MList::Util=sum -alne 'print sum @F'

Convert character types

Convert non-ASCII characters into SGML/HTML/XML-style decimal numeric character references (e.g. Ş becomes Ş):

perl -C -pe 's/([^\x00-\x7f])/sprintf("&#%d;", ord($1))/ge;'

Convert (hexa)decimal numeric character references to UTF-8:

perl -C -pe 's/&\#(\d+);/chr($1)/ge;s/&\#x([a-fA-F\d]+);/chr(hex($1))/ge;'

Deserialize JSON file

Assume one legal JSON record per line

zcat file.json.gz | perl -MLWP::Simple -MJSON -se 'while(<STDIN>) {$ref = decode_json($_); print "$ref->{attrX}\t$ref->{xttrY}\n"}' > out.tsv

pass a parameter

var=bar

perl -sne 'chomp; print "$_ " . $foo;' -- -foo=${var} file.txt

replace term from a 2-column dictionary file

cat file.txt | \

perl -sne 'open DICT, “<$dict"; while(<DICT>) {($new,$prev)=split ; $regex{$prev}=$new;} $prevs = join "|", keys %regex ; while (<STDIN>) { s/($prevs)/$regex{$1}/g; print}' \

-- -dict=dict.tsv

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