alias.sh

Shall高级编程

#!/bin/bash
# alias.sh

shopt -s expand_aliases
# Must set this option, else script will not expand aliases.


# First, some fun.
alias Jesse_James='echo "\"Alias Jesse James\" was a 1959 comedy starring Bob Hope."'
Jesse_James

echo; echo; echo;

alias ll="ls -l"
# May use either single (') or double (") quotes to define an alias.

echo "Trying aliased \"ll\":"
ll /usr/X11R6/bin/mk*   #* Alias works.

echo

directory=/usr/X11R6/bin/
prefix=mk*  # See if wild card causes problems.
echo "Variables \"directory\" + \"prefix\" = $directory$prefix"
echo

alias lll="ls -l $directory$prefix"

echo "Trying aliased \"lll\":"
lll         # Long listing of all files in /usr/X11R6/bin stating with mk.
# An alias can handle concatenated variables -- including wild card -- o.k.




TRUE=1

echo

if [ TRUE ]
then
  alias rr="ls -l"
  echo "Trying aliased \"rr\" within if/then statement:"
  rr /usr/X11R6/bin/mk*   #* Error message results!
  # Aliases not expanded within compound statements.
  echo "However, previously expanded alias still recognized:"
  ll /usr/X11R6/bin/mk*
fi  

echo

count=0
while [ $count -lt 3 ]
do
  alias rrr="ls -l"
  echo "Trying aliased \"rrr\" within \"while\" loop:"
  rrr /usr/X11R6/bin/mk*   #* Alias will not expand here either.
                           #  alias.sh: line 57: rrr: command not found
  let count+=1
done 

echo; echo

alias xyz='cat $0'   # Script lists itself.
                     # Note strong quotes.
xyz
#  This seems to work,
#+ although the Bash documentation suggests that it shouldn't.
#
#  However, as Steve Jacobson points out,
#+ the "$0" parameter expands immediately upon declaration of the alias.

exit 0