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PC Technician code to change text in multiple files

In this code example - I wanted to make global changes to multiple files in a directory structure using unix commands. This involves the use of two commands - "find" and "sed". I wanted to write a general shell script to accomplish this. I found one example that used a combination of first getting a list of files in a directory and its directory substructure and then processing this list with a "do" loop which used the sed command. I then came up with a simpler way to do this without the "do" loop which also involved creating a temp file and then moving it back to the original file (seems a bit clumsy).

So here's what I did - in the shell script.


1. Read in the starting directory where I wanted to change the files.
2. Read in the text strings - the old the replacement strings.
3. Develop the command to perform the work.
   This is described in the code example below:

#!/bin/sh
#This script will replace a string of characters ( with a new string)
#in all regular files starting from a user specified directory path and below.

echo "Enter the Full DIR path[/home/development ......] "

read FULL_DIR

echo " Enter the text to be replaced "
read OLDTEXT

echo " Enter the new text "
read NEWTEXT

#In command below -  the colon in the sed commmand is a delimiter
# and the {} braces are enclosed in single quotes to protect them 
# from interpretation as shell script punctuation. The backslash 
# also protects the semi-colon mis-interpretation  by the shell 
# script.
# The {} braces enclose commands to sed or in this case - the 
# list of files found by the find command, so sed looks and 
# replaces any OLDTEXT, if found, with the NEWTEXT
# and saves the file with the NEWTEXT substitution - which the 
# flag -i tells sed to do. If you want to be safe, it is suggested 
# that the -i flag contain an extension (like .bak  coded as -i.bak)
# so the original file is saved as  xxx.bat where xxx is the name 
# of the original file passed to sed. The only problem here is -  
# all files passed to sed via the find command - a backup file 
# is created.
# So if you have a 1000 files - you will wind up with 2000 
# files - 1000 of which will have the extension .bak, whether 
# or not it was changed by sed.

find $FULL_DIR  -type f   -exec sed -i "s:${OLDTEXT}:${NEWTEXT}:g" '{}' \;

#If you want the backup file option then comment out the above command and
# uncomment the command below:

#find $FULL_DIR  -type f   -exec sed  -i.bak "s:${OLDTEXT}:${NEWTEXT}:g" '{}' \;



P.S.
By the way, when I tried the global changes using the
code based on first getting the list of files and then the
do-loop to process the list  -  caused a problem.  See the code
below:
 
--------------------------------------------------------------------------------- 
list=`find $FULL_DIR   -type f ` 
for file in ${list} 
do 
#In the command below -  the colon is a delimiter in the sed command
# and obviously the old and new text cannot have this character in the strings.
 
sed s:"${OLDTEXT}":"${NEWTEXT}":g ${file} > /tmp/temp.txt 
mv /tmp/temp.txt ${file} 
done 
 
---------------------------------------------------------------------------------- 
 
 
What happened was the "mv" command changed file permissions
on the .cgi and .pl  files to read only , ie,  it lost the execute bit on these 
files as a result of the creation of the temp file and the subsequent move command. 
So I then tried  a global change to these files using the "chmod"
command, ie,  I tried this:

chmod -R 755 *.cgi
 
which theorectically should work to recursively change all files 
ending  in .cgi to mode 755 for the current directory and below.
Well it didn't, so I then tried a variation - which is coded as shown:

find . -type f -name '*.cgi' -exec chmod 755 {} \;  

And this worked just fine. Note the similarity between this command and 
the find/sed command in the shell script in the white box above.

If you need more info on shell scripting try HERE - Great tutorial site.

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