Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
exit 0
Piping output to a read, using echo to set variables will fail.
However, piping the output of cat does seem to work.
cat file1 file2 |
while read line
do
echo $line
done
Filesystem
cd
The familiar cd change directory command finds use in scripts where execution of a command
requires being in a specified directory.
(cd /source/directory && tar cf − . ) | (cd /dest/directory && tar xpvf −)
[from the previously cited example by Alan Cox]
The −P (physical) option to cd causes it to ignore symbolic links.
cd − changes to $OLDPWD, the previous working directory.
The cd command does not function as expected when presented with two forward
slashes.
bash$ cd //
bash$ pwd
//
The output should, of course, be /. This is a problem both from the command line and
in a script.
pwd
Print Working Directory. This gives the user's (or script's) current directory (see Example 11−7). The
effect is identical to reading the value of the builtin variable $PWD.
pushd, popd, dirs
This command set is a mechanism for bookmarking working directories, a means of moving back and
forth through directories in an orderly manner. A pushdown stack is used to keep track of directory
names. Options allow various manipulations of the directory stack.
pushd dir−name pushes the path dir−name onto the directory stack and simultaneously
changes the current working directory to dir−name
popd removes (pops) the top directory path name off the directory stack and simultaneously changes
the current working directory to that directory popped from the stack.
Chapter 11. Internal Commands and Builtins 131