Shell Scripting: Expert Recipes for Linux, Bash, and More

Tab Completion

All of the modern shells have command and filename completion via the <TAB> key. Bourne shell and csh do not, but ksh, bash, tcsh, and zsh all have tab completion to varying degrees. The basic principle in all of these shells is the same; you type the start of the word, hit the <TAB> key twice, and the list of possible commands or files is displayed. The actual details differ in implementation, so a brief overview of how to get things done in each of these shells follows.

ksh

Typing ca and then hitting <TAB> twice results in a list rather like that produced by the select command. Each item is numbered so you simply enter the number that relates to your choice followed by another <TAB>. For example, ca could be the start of cancel, callgrind_annotate, or any of these other possibilities.

ksh$ ca<TAB><TAB>
 1) /usr/bin/cancel
 2) /usr/bin/callgrind_annotate
 3) /usr/bin/cameratopam
 4) /usr/bin/callgrind_control
 5) /usr/bin/cancel.cups
 6) /usr/bin/cal
 7) /usr/bin/captoinfo
 8) /usr/bin/catchsegv
 9) /usr/bin/card
10) /usr/sbin/cacertdir_rehash
11) /usr/sbin/callback
12) /bin/cat
6<TAB>
ksh$ /usr/bin/cal
     March 2011
Su Mo Tu We Th Fr Sa
       1  2  3  4  5
 6  7  8  9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30 31
$

Filename completion works in exactly the same way:

ksh$ cat /etc/host<TAB><TAB>
1) host.conf
2) hosts
3) hosts.allow
4) hosts.deny
4<TAB>
ksh$ cat /etc/hosts.deny

tcsh

tcsh acts in much the same way, but the options are ...