UNIX for Dummies Questions & Answers

$ cat file1
i am unix guy
$ sed 's/i /I/g' file1
Iam unix guy
$

/\bWORD\b/                          # word is framed by blanks
/\<WORD\>/                          # match whole word inside < >
/[[:blank:]]WORD[[:blank:]]/        # word is framed by blanks (alternate)

sed -e 's/i/I/g' -e 's/\([a-zA-Z].*\)I\([a-zA-Z].*\)/\1i\2/g' file

#!/usr/bin/env sh

# @(#) s1       Demonstrate changing case considering "word" boundaries.

set -o nounset
echo

debug=":"
debug="echo"

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

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

echo

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

echo
echo " Results from sed:"
sed 's_\<i\>_I_g' $FILE

exit 0

% ./s1

(Versions displayed with local utility "version")
GNU bash 2.05b.0
GNU sed version 4.1.2

 Input file:
i'm the big brother.
i never drink water, i
only drink beer.
i've got to do this job.
Yes, i can do it.

 Results from sed:
I'm the big brother.
I never drink water, I
only drink beer.
I've got to do this job.
Yes, I can do it.