Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
# Uses 'awk' to strip off the filename.
The mcookie command gives yet another way to generate a "unique" filename.
Example 12−43. Filename generator
#!/bin/bash
# tempfile−name.sh: temp filename generator
BASE_STR=`mcookie`
POS=11
LEN=5
prefix=temp
# 32−character magic cookie.
# Arbitrary position in magic cookie string.
# Get $LEN consecutive characters.
# This is, after all, a "temp" file.
# For more "uniqueness," generate the filename prefix
#+ using the same method as the suffix, below.
suffix=${BASE_STR:POS:LEN}
# Extract a 5−character string, starting at position 11.
temp_filename=$prefix.$suffix
# Construct the filename.
echo "Temp filename = "$temp_filename""
# sh tempfile−name.sh
# Temp filename = temp.e19ea
units
exit 0
This utility converts between different units of measure. While normally invoked in interactive mode,
units may find use in a script.
Example 12−44. Converting meters to miles
#!/bin/bash
# unit−conversion.sh
convert_units () # Takes as arguments the units to convert.
{
cf=$(units "$1" "$2" | sed −−silent −e '1p' | awk '{print $2}')
# Strip off everything except the actual conversion factor.
echo "$cf"
}
Unit1=miles
Unit2=meters
cfactor=`convert_units $Unit1 $Unit2`
quantity=3.73
result=$(echo $quantity*$cfactor | bc)
echo "There are $result $Unit2 in $quantity $Unit1."
# What happens if you pass incompatible units,
#+ such as "acres" and "miles" to the function?
Chapter 12. External Filters, Programs and Commands 212