Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
printf "Pi to 9 decimal places = %1.9f" $PI # It even rounds off correctly.
printf "\n"
# Prints a line feed,
# equivalent to 'echo'.
printf "Constant = \t%d\n" $DecimalConstant # Inserts tab (\t)
printf "%s %s \n" $Message1 $Message2
echo
# ==========================================#
# Simulation of C function, 'sprintf'.
# Loading a variable with a formatted string.
echo
Pi12=$(printf "%1.12f" $PI)
echo "Pi to 12 decimal places = $Pi12"
Msg=`printf "%s %s \n" $Message1 $Message2`
echo $Msg; echo $Msg
# As it happens, the 'sprintf' function can now be accessed
# as a loadable module to Bash, but this is not portable.
exit 0
Formatting error messages is a useful application of printf
E_BADDIR=65
var=nonexistent_directory
error()
{
printf "$@" >&2
# Formats positional params passed, and sents them to stderr.
echo
exit $E_BADDIR
}
cd $var || error $"Can't cd to %s." "$var"
read
# Thanks, S.C.
"Reads" the value of a variable from stdin, that is, interactively fetches input from the keyboard.
The −a option lets read get array variables (see Example 26−3).
Example 11−2. Variable assignment, using read
#!/bin/bash
echo −n "Enter the value of variable 'var1': "
# The −n option to echo suppresses newline.
read var1
# Note no '$' in front of var1, since it is being set.
Chapter 11. Internal Commands and Builtins 126