Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
# The "strings" command lists strings in binary files.
# Output then piped to "grep", which tests for desired string.
do
echo $word
done
# As S.C. points out, the above for−loop could be replaced with the simpler
# strings "$2" | grep "$1" | tr −s "$IFS" '[\n*]'
# Try something like "./bin−grep.sh mem /bin/ls" to exercise this script.
exit 0
More of the same.
Example 10−8. Listing all users on the system
#!/bin/bash
# userlist.sh
PASSWORD_FILE=/etc/passwd
n=1 # User number
for name in $(awk 'BEGIN{FS=":"}{print $1}' < "$PASSWORD_FILE" )
# Field separator = : ^^^^^^
# Print first field ^^^^^^^^
# Get input from password file ^^^^^^^^^^^^^^^^^
do
echo "USER #$n = $name"
let "n += 1"
done
# USER #1 = root
# USER #2 = bin
# USER #3 = daemon
# ...
# USER #30 = bozo
exit 0
A final example of the [list] resulting from command substitution.
Example 10−9. Checking all the binaries in a directory for authorship
#!/bin/bash
# findstring.sh:
# Find a particular string in binaries in a specified directory.
directory=/usr/bin/
fstring="Free Software Foundation" # See which files come from the FSF.
for file in $( find $directory −type f −name '*' | sort )
do
strings −f $file | grep "$fstring" | sed −e "s%$directory%%"
# In the "sed" expression,
Chapter 10. Loops and Branches 107