7 – Seeing The World As The Shell Sees It

current working directory) before the echo command is executed. When the enter key is

pressed, the shell automatically expands any qualifying characters on the command line

before the command is carried out, so the echo command never saw the “*”, only its ex-

panded result. Knowing this, we can see that echo behaved as expected.

Pathname Expansion

The mechanism by which wildcards work is called pathname expansion. If we try some

of the techniques that we employed in our earlier chapters, we will see that they are really

expansions. Given a home directory that looks like this:

[me@linuxbox ~]$ ls

Desktop ls-output.txt Pictures Templates

Documents Music Public Videos

we could carry out the following expansions:

[me@linuxbox ~]$ echo D*

Desktop Documents

and:

[me@linuxbox ~]$ echo *s

Documents Pictures Templates Videos

or even:

[me@linuxbox ~]$ echo [[:upper:]]*

Desktop Documents Music Pictures Public Templates Videos

and looking beyond our home directory:

[me@linuxbox ~]$ echo /usr/*/share

/usr/kerberos/share /usr/local/share