jrep

A new generation grep written in node/javascript.

Think of awk & sed with javascript syntax.

Very useful for bash scripting and devops works. Very handy and extermly flexible.

🧤 Usage

jrep <filter1> <filter2> ...

• Each <filter>
  • is a string transformation (a map callback)
  • is the body of a javascript function with arg x
• The s are applied sequentially on each line in the piped content.
• In case of exception in any of the s, that line is removed.

🎩 Built-in primitives

| primitive |meaning| usage | | ----------- |----| ----------- | | ✨ RE1 ✨ |find/replace regexp| RE1( <regular expression with parentheses> ) | | ✨ RER ✨ |find + custom replace| RER( regexp. , a string with p[1],p[2], ... ) | | || |

⌨️ Example

uname -a | jrep 'x.replace(/a/g, "O")'

⛑ Practical examples

• Extract pids ps aux|jrep 'x.substring(12,24)'
• Extract the filenames in a find command:

find .| jrep '/([^\/]*)$/.exec(x)[1]'

• Using env for filter names: Another way to write it is to use bash env vars for filter names. It is will be also more reusable. A more readable notation:

EXTRACT_BASENAME='/([^\/]*)$/.exec(x)[1]'
find / | jrep $EXTRACT_BASENAME | head

• The PSAUX_PID can extract the PID from the output of the commonly used ps aux command (tested on MacOS). Is can be used to extract other columns

PSAUX_PID='[.../([^ ]*) * (\d*) *(\d+\.\d+) *(\d+\.\d+) *(\d+) *(\d+) *([^ ]+) +([^ ]+) +([^ ]+) +([^ ]+) +(.*)$/.exec(x)].slice(1)[1]'
ps aux | jrep "$PSAUX_PID"

• Another usage of PSAUX_PID:

ps aux | grep -v grep | grep http-server | jrep "$PSAUX_PID" | xargs kill

• Emulate cut command: ps aux|jrep 'x.substring(12,24)'
• Pairs of pid and their running time:

ps aux|jrep "{time=x.substring(70,78); pid=x.substring(15,24); return pid+':'+time;}"

• Sort PIDs based on runing time:

ps aux|jrep "{time=x.substring(70,78); pid=x.substring(15,24); return time + ':' + pid;}"|sort

• Replace letters with frog: (such a useful scenario)

uname -a | jrep 'x.replace(/[a-z]/g, "🐸")'

• Using ✨ built-in primitives: RE1 ✨. The following two are equivalent:

ps aux | jrep 'RE1(".*(python.*)")'
ps aux | jrep '/.*(python.*)/.exec(x)[1]'

• The following three are equivalent

ps aux | jrep 'RE1("(.*python.*)")'
ps aux | jrep '/(.*python.*)/.exec(x)[1]'
ps aux | grep -e python

• Using ✨ built-in primitive RER ✨. Replace python in filenames with emojies.

find .. | jrep 'RER("(.*)python(.*)", "p[1]+\"🐍🐍\"+p[2]")'

🐻 Find jrep on npm: jrep1

💡 Some suggested use cases

• Eliminate usage of obscure aommands such as awk, sed, perl
• Unified solution without usual tools cut, grep
• Replace a matched regular expression with given custom ccombination (See RER)
• Extract part of an RE1 pattern (See RE1)

🤝

• 👋 Feel free to send Pull Requests.
• 👋 Feel free to request features.

✨ Pros

• 👍 transform (map) text in linux pipes
• 👍 filter text in linux pipes
• 👍 concise
• 👍 versatile
• 👍 exteremly flexible
• 👍 customisable
• 👍 prebuilt primitive operations
• 👍 Super lightweight
• 👍 Zero npm dependencies
• 👍 Docker version available

Cons

• 👎 Needs node installed on the system. 👍 If you don't want to install node, an alternative is to use docker.

📌 Requirements

• NodeJS (tested on node 12 and node v16.15.0)

💻 Installation

• 🐻 npm

npm i -g jrep1
# test:
uname -a | jrep 'x.replace("a", "O")'

• 💻 MacOS , Linux

git clone https://github.com/sohale/jrep.git
./jrep/scripts/install-macos.bash

• 🐻 npm jrep1 on npm

npm install -g jrep

• 🐱 yarn

yarn install -g jrep

📚 Example Usage

Also see test/e2e-test.bash

• 🐳 docker No need to install Node

find / | \
    docker run -i sohale/jrep:latest \
       '/\/([^\/]*\.py)$/.exec(x)[1]'

• ⌨️ npx

uname -a | npx jrep 'x.replace("a", "O")'

• 📡 bash (on the fly)

find .. | \
    node -e "$(curl -L https://raw.githubusercontent.com/sohale/jrep/main/src/jrep.js | tail -n +2))" '' \
       '/\/([^\/]*\.py)$/.exec(x)[1]'

• requires NodeJS (tested on node 12) to be installed on your system.

💻 Development ⌨️

docs/internals.md

📚 Tutorial

(comming soon)