Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
dirs lists the contents of the directory stack (compare this with the $DIRSTACK variable). A
successful pushd or popd will automatically invoke dirs.
Scripts that require various changes to the current working directory without hard−coding the
directory name changes can make good use of these commands. Note that the implicit $DIRSTACK
array variable, accessible from within a script, holds the contents of the directory stack.
Example 11−7. Changing the current working directory
#!/bin/bash
dir1=/usr/local
dir2=/var/spool
pushd $dir1
# Will do an automatic 'dirs' (list directory stack to stdout).
echo "Now in directory `pwd`." # Uses back−quoted 'pwd'.
# Now, do some stuff in directory 'dir1'.
pushd $dir2
echo "Now in directory `pwd`."
# Now, do some stuff in directory 'dir2'.
echo "The top entry in the DIRSTACK array is $DIRSTACK."
popd
echo "Now back in directory `pwd`."
# Now, do some more stuff in directory 'dir1'.
popd
echo "Now back in original working directory `pwd`."
exit 0
Variables
let
The let command carries out arithmetic operations on variables. In many cases, it functions as a less
complex version of expr.
Example 11−8. Letting let do some arithmetic.
#!/bin/bash
echo
let a=11
# Same as 'a=11'
let a=a+5 # Equivalent to let "a = a + 5"
# (double quotes and spaces make it more readable)
echo "11 + 5 = $a"
let "a