Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
a=`echo "HELLO" | tr A−Z a−z`
See also Example 12−15, Example 12−2, Example 12−32, and Example 12−33.
Be aware that echo `command` deletes any linefeeds that the output of command generates.
The $IFS (internal field separator) variable normally contains \n (linefeed) as one of its set of
whitespace characters. Bash therefore splits the output of command at linefeeds into arguments to
echo. Then echo outputs these arguments, separated by spaces.
bash$ ls −l /usr/share/apps/kjezz/sounds
−rw−r−−r−− 1 root root 1407 Nov 7 2000 reflect.au
−rw−r−−r−− 1 root root 362 Nov 7 2000 seconds.au
bash$ echo `ls −l /usr/share/apps/kjezz/sounds`
total 40 −rw−r−−r−− 1 root root 716 Nov 7 2000 reflect.au −rw−r−−r−− 1 root root 362 Nov 7
This command is a shell builtin, and not the same as /bin/echo, although its
behavior is similar.
bash$ type −a echo
echo is a shell builtin
echo is /bin/echo
printf
The printf, formatted print, command is an enhanced echo. It is a limited variant of the C language
printf() library function, and its syntax is somewhat different.
printf format−string... parameter...
This is the Bash builtin version of the /bin/printf or /usr/bin/printf command. See the
printf manpage (of the system command) for in−depth coverage.
Older versions of Bash may not support printf.
Example 11−1. printf in action
#!/bin/bash
# printf demo
PI=3.14159265358979
DecimalConstant=31373
Message1="Greetings,"
Message2="Earthling."
echo
printf "Pi to 2 decimal places = %1.2f" $PI
echo
Chapter 11. Internal Commands and Builtins 125