Bash

Bash

BASH

#!/bin/bash -e

echo $@

first_arg=shift

Some commands:

  • nproc: returns number of processing units available to the process
 

awk

General pattern:

awk -F "." "/regex1/{ print $2 } /regex2/{ print $2 }" file1 file2 ... fileN

Special control variables:

  • FS: field separator (default: whitespace)
  • RS: record separator (default: new line \n)
  • OFS: output field separator
  • ORS: output record separator

Special information variables:

  • NF: number of fields in the current record
  • NR: number of record since the beginning
  • FILENAME: current file being processed
  • FNR: number of record of the current file

Field variables:

  • $0: whole line
  • $(x): Field number x. Can be $($(1)). Writing to field variables forces a regeneration of $0. Can write to non-existent fields.

Operators, mostly C operators and in addition:

  • ~ regular expression match

Assign values in BEGIN action. Multiple actions can be combined:

awk 'BEGIN{FS='.'; RS="!"} /up/{print $1} /down/{ print $1 }' input_file.txt
 

sed

Replace all occurences of something into nothing:

for I in *.txt; do sed -i "s/something/nothing/" $I; done
 

Tcl/Tk

From here, find the right event to bind to:

package require Tk
pack [text .t -bg white]
bind .t <KeyPress> {puts "You pressed the key named: %K "}
bind .t <ButtonPress> {puts "You pressed button: %b at %x %y"}
 

Emacs

Ctrl+n next character
Ctrl+p previous character
Meta+n next word
Meta+p previous word
 

Dotty

Git

Nice tutorials:

Multipurpose commands:

  • git checkout:
    • get a particular commit
    • change to a branch
  • git branch:
    • get list of branches
    • create a new branch

Main commands:

# Repo creation
git clone /repo/path .
git init .
# Adding changes
git add file
git commit -m "Commit message" # Add list of files for targeted commit
# Status
git status
git log
git log --graph --decorate --abbrev-commit --all --date=local --pretty=format:\"%C(auto)%h%d %C(blue)%an %C(green)%cd %C(red)%GG %C(reset)%s\" --date=local

Fixing the last commit:

git add forgot_this_file.txt
git commit --amend 
# Add --no-edit above to skip message prompt

Syntax for versions:

  • ~ : parent of version
  • ^ : Selects among multiple parents (as in a merge)