This article introduces some lesser known Bash Functions and Commands which are also included in the subject area of the LPI certifications. Please use the feedback function at the end of this article to share any other tips not discussed here.
cd -- change to the previous directory
set +o history- turn off Bash History (.bash_history)
set -o history- turn on Bash History again
apropos <keyword>- search the man pages
- Example:
$ apropos telnet cacaserver (1) - telnet server for libcaca telnet (1) - user interface to the TELNET protocol telnet.netkit (1) - user interface to the TELNET protocol
whatis <keyword>- To display the man page description
- Example:
$ whatis crontab crontab (5) - tables for driving cron crontab (1) - maintain crontab files for individual users (Vixie Cron)
- Both man pages can be retrieved using:
man crontab 5; man crontab 1 pr- Print the text file via the command line
nl- To number the rows
- Example:
$ cat test.txt | nl 1 das ist zeile 1 2 und das zeile 2
fmt- Format text with a specified width
- Example:
$ fmt --width=5 test.txt this is row 1 and this is row 2
cut -d ' ' -f1- Crop output line by line
- -d … delimiter
- -f1 … select field 1
- Example:
$ cut -d ' ' -f1 test.txt this and
sort- sorts a text file
uniq- removes doubled row. It makes sense to remove any duplicates following a “sort”.
tr- performs substitutions by (“translate”).
- Example:
cat test.txt | tr '[:lower:]' '[:upper:]' DAS IST ZEILE 1 UND DAS ZEILE 2
tr- performs substitutions by (“translate”).
- Example:
cat test.txt | tr '[:lower:]' '[:upper:]' THIS IS ROW 1 AND THIS IS ROW 2
[Str]+[R]- Browse the command history
history- Display command history
find / -iname <Datei/Verzeichnisname>- Browse the file/directories with no case sensitivity. A case-sensitive search can be done using “-name”.
find / -type f -print0 | xargs -0 grep -i <keyword>- Search for specific text in all files /Keyword
find -L . -type l- Find broken symbolic links(that do not have a valid destination)
bash -x <scriptname>- Debugging from Bash-Scripts
rename- Rename the files with common names
- Example:
ls file-1 file-2 file-3 rename 's/-/_/' file-* ls file_1 file_2 file_3
