Bash tricks – Some of the useful bash shortcuts · #!pkk

Bash tricks – Some of the useful bash shortcuts

Set the default text editor

echo ‘export EDITOR=“vim”’ >> ~/.bashrc

Change the default history size (number of commands that are saved)

echo “HISTSIZE=2000” >> ~/.bash_profile
echo “HISTFILESIZE=2000” >> ~/.bash_profile

Find and run a command from history

history | grep search_keyword
!n #where n is the command number

or you can use CTRL-r

Create new nested directories at once

mkdir -p /tpm/this/and/that/will/be/created

Find files and execute a command on them
```
find . -name ‘*.php’ | xargs wc -l
```

Loop through a command numerous times

for i in {1..10} ; do touch filenumber${i} ; done;
#will create 10 files named file_number_1 .. file_number_10

Shorter way of doing above :

touch file_number_{1..10}

Synchronize a local direcotry with a remote one

$ rsync -r -a -z -v -e “ssh -l remoteuser” –delete /local/path host.name:/remote/path

Delete all files in directory (shortcut for directories with large amount of files)
```
mkdir empty
rsync -a –delete empty/ target_directory/
```
Print file by columns using awk
```
awk -F”delimiter” ‘{ print $1 }’ /path/to/file
```
It will print first column, determining columns by “delimiter”
Real life exapmle, print all usernames in system:
```
cat /etc/passwd | awk -F":" '{ print $1 }'
```
Replace Xth column in a row using awk
```
awk -F”delimiter” ‘$X=“replace”’  /path/to/file
#X - is the number of column
```
It will print first column, determining columns by “delimiter”
Real life exapmle, print all usernames in system and replace the password column with a dash:
```
cat /etc/passwd | awk -F":" '{  $2=" - "; print $1 $2 }'
```
Simple way to change date:
```
date +%Y%m%d -s “20081128”
```
Simple way to change time:
```
date +%T -s “10:13:13”
```

Grep recursively :

grep -R  “searchword” /path/to/search

Find out which directories consume most of the disk space:

find / -mount -size +1024k -type f -exec ls -la {} \;|sort -rnb -k 5 | less

If You want more, check this cheatsheet.