UNIX for Dummies Questions & Answers

#!/usr/bin/env sh

# @(#) s1       Demonstrate expressions that match omitted characters.

set -o nounset
echo

debug=":"
debug="echo"

## The shebang using "env" line is designed for portability. For
#  higher security, use:
#
#  #!/bin/sh -

## Use local command version for the commands in this demonstration.

echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version bash

echo

FILE=${1-data1}
echo " Input file $FILE:"
cat $FILE

echo
echo " Results from grep:"
grep -vi "s" $FILE

echo
echo " Results from more complicated expression:"
grep '^[^sS]*$' $FILE

exit 0

% ./s1

(Versions displayed with local utility "version")
GNU bash 2.05b.0

 Input file data1:
Line number one.
a
s
S
Line that shuld match character at end: s
S beginning on a line.
Line with s and S in the middle.
Line omitting the character for which we look.
Last line.

 Results from grep:
Line number one.
a
Line omitting the character for which we look.

 Results from more complicated expression:
Line number one.
a
Line omitting the character for which we look.