pjs

pjs is a command-line tool for filtering and transforming text, similar to awk. You provide it powerful one-line snippets written in vanilla JavaScript. It supports many input formats, including plain text, CSV, JSON, HTML, and XML.

pjs works by generating a complete JS program from the provided script, and feeding it each line of standard input. The statically generated program can be reviewed with --explain.

See the examples section below to see what pjs can do. For complete documentation, read the manual or run man pjs.

Installing

Install the pjs command with npm:

npm install -g pjs-tool

If npm is not available on your environment, you can download a standalone executable. You will still need node installed.

Examples

Click on an example to run it in your browser at the pjs playground.

Transforming Examples

Convert a file to upper-case:

cat input.txt | pjs '_.toUpperCase()'

Print the second field of each line (in this example, the PIDs):

ps aux | pjs '$1'

Print all fields after the 10th (in this example, the process names):

ps aux | pjs '$.slice(10).join(" ")'

Remove trailing whitespace from each line in a file:

cat document.txt | pjs '_.replace(/\s*$/, "")'

Filtering Examples

Given a list of numbers, print only numbers greater than 5:

seq 1 10 | pjs '_ > 5'

Given a list of numbers, print only even numbers:

seq 1 10 | pjs '_ % 2 == 0'

Print the last 4 lines of a file (like tail):

seq 1 10 | pjs --after 'LINES.slice(-4).join("\n")'

Print every other line of a file:

cat input.txt | pjs 'COUNT % 2 == 1'

Given a list of filenames, print the files that actually exist:

cat filenames.txt | pjs 'fs.existsSync(_)'

Given a list of filenames, print the files that are under one kilobyte in size:

cat filenames.txt | pjs 'fs.statSync(_).size < 1000'

Summarizing Examples

Manually count the lines in the input (like wc -l):

cat input.txt | pjs '{ count++ }' --after 'count'

Same as above, but using the built-in COUNT variable:

cat input.txt | pjs --after 'COUNT'

Count the unique lines in the input:

cat input.txt | pjs --before 'let s = new Set()' '{ s.add(_) }' --after 's.size'

Manually sort the lines of the input (like sort)

cat input.txt | pjs --before 'let lines = []' '{ lines.push(_) }' --after 'lines.sort().join("\n")'

Same as above, but using the built-in LINES variable:

cat input.txt | pjs --after 'LINES.sort().join("\n")'

CSV Examples

Given a grades.csv file that looks like this:

name,subject,grade
Bob,physics,43
Alice,biology,75
Alice,physics,90
David,biology,85
Clara,physics,78

Print only the third column:

cat grades.csv | pjs --csv '$2'

Print the grades using the column header:

cat grades.csv | pjs --csv-header '_.grade'

Print the names of students taking biology:

[cat grades.csv | pjs --csv-header '_.subject == "biology" && _.name'](https://aduros.com/pjs/#%7B%22command%22%3A%22pjs%20--csv-header%20'.subject%20%3D%3D%20%5C%22biology%5C%22%20%26%26%20.name'%22%2C%22input%22%3A%22name%2Csubject%2Cgrade%5CnBob%2Cphysics%2C43%5CnAlice%2Cbiology%2C75%5CnAlice%2Cphysics%2C90%5CnDavid%2Cbiology%2C85%5CnClara%