JohnCrickett / UsefulScriptTidBits

Various useful scripting tidbits

Useful script tidbits

Bash Scripts

Simple CPU monitoring per core

use top to get the cpu usuage by core every second. First set top to show each core, run top and press 1, then Shift + W

top -b -d 1 | grep %Cpu

Find files with extension and run a command against those files

find . -name "*.txt" -type f -exec head -n2 {} \;

For example, find all files in a directory tree where the name matches a pattern and grep them:

find . -name \*.txt -exec grep pattern {} +

Sorting some output and getting the first and last values (lines)

<some command generating output> | sort | sed -n '1p;$p'

<some command generating output> | sort | tee >(head -n 1) >(tail -n 1) >/dev/null

Extract lines beginning with a pattern

sed -n -e '/^{"pattern"/p' infile.txt

Remove space between first and second column of a text file:

sed -r 's/[[:blank:]]+//1' infile.txt replace the 1 with another number to do other columns

Find the number of files in a dir

find DIR_NAME -type f | wc -l replace DIR_NAME with the directory

Kill all processes matching a pattern

ps aux |grep pattern_of_process |awk '{print $2}' |xargs kill

Globbing

Files matching a pattern (.txt extention)

ls *.txt

Extended Globbing

First turn it on:

shopt -s extglob

Files not matching a pattern (not .txt extension)

ls !(*.txt)

File matching one of a set of patterns

ls @(*txt|*log)

Squishing JSON

sed 's/\"/\\\"/g' somefile.json | tr -d '\n' | tr -d '[[:blank:]]'