Boost Your Unix Productivity: 10 Essential Shell Tricks You Need

1. Filename Autocompletion

Filename autocompletion saves you from typing long, error‑prone names. Identify your shell first (e.g., echo $0 or ps -p $$).

C Shell : Enable with set filec. Press Esc after typing part of a name to complete it.

Bash : Autocompletion is on by default and uses the Tab key. Press Tab once to complete a unique name; press twice to list all matches.

Korn Shell : Completion depends on the EDITOR variable. If EDITOR=vi, press Esc followed by \. If EDITOR=emacs, press Esc twice.

2. History Expansion

The !$ operator reuses the last argument of the previous command, which is handy for repeating long filenames.

$ grep pickles this-is-a-long-lunch-menu-file.txt
$ vi !$

3. Reusing Previous Arguments

Combine !$ with !:1 to select specific arguments from the prior command. Example:

$ mv kxp12.c file_system_access.c
$ ln -s !$ !:1

4. Directory Navigation with pushd and popd

pushd

adds the current directory to a stack and changes to a new one; popd returns to the previous directory. Use dirs to view the stack.

$ pushd .
$ pushd /etc
$ pushd /var
$ pushd /usr/local/bin
$ dirs
$ popd
$ popd
$ popd
$ popd

You can rotate the stack with pushd +n or pushd -n.

5. Finding Large Files

Use df to see disk usage per volume. $ df Search for files larger than 10 MB with find:

$ find / -size +10000k -xdev -exec ls -lh {} \;

6. Creating Temporary Files without an Editor

Redirect output from cat to create a file:

$ cat > my_temp_file.txt
This is my temp file text
^D
$ cat my_temp_file.txt

Append to an existing file with >>:

$ cat >> my_temp_file.txt
More text
^D
$ cat my_temp_file.txt

7. Using curl

curl

retrieves data via many protocols. Download a file with the -o option:

$ curl -o archive.tar http://www.somesite.com/archive.tar

8. Effective Use of Regular Expressions

Regular expressions (regex) define pattern strings for matching text. Common metacharacters include:

^ – start of line

$ – end of line

\ – escape next character

[] – character class

[^] – negated class

. – any single character (except newline)

* – zero or more of the preceding element

{x,y} – between x and y repetitions

{x} – exactly x repetitions

{x,} – x or more repetitions

Typical grep examples:

$ grep '^From: ' /usr/mail/$USER
$ grep '[a-zA-Z]' search-file.txt
$ grep '[^a-zA-Z0-9]' search-file.txt
$ grep '[0-9]{3}-[0-9]{4}' search-file.txt
$ grep '^.$' search-file.txt
$ grep '^.[a-z][a-z]' search-file.txt

9. Determining the Current User

Run whoami to print the current username.

$ whoami
John

Example script to prevent running as root:

if [ $(whoami) = "root" ]
then
  echo "You cannot run this script as root."
  exit 1
fi

10. Data Processing with awk

awk

excels at line‑oriented text processing.

Length of each line: $ awk '{ i = length($0); print i }' text Find position of "ing": $ awk '{ i = index($0,"ing"); print i }' text Tokenize a line into words:

$ awk 'BEGIN { i = 1 } { n = split($0,a," "); while (i <= n) { print a[i]; i++; } }' text

Summarize CSV data (sales example): $ awk -F, '{print $1,$2+$3+$4}' sales Result:

Gene 42
Dawn 50
Renee 46
David 46