need help in modifying the contents of a text file

akk8q8 · #1 (**permalink**) 02-23-04, 15:11

Hello,
I am a novice in shell scripting. Need help in modifying the contents of a text file.

the contents of the text file are:
[foldername.session name]
$$deptno=10

I want to change the value $$deptno=40. Cud any one suggest a shell script which prompts the user for the value and updates deptno with the value.

Finally ...the shell script every time its run it sud modify the value of $$deptno as defined by the user.

Thanking you,
ak

aigles · #2 (**permalink**) 02-23-04, 15:35

Try and adapt the following code :

Code:

#
# Read new deptno value
#
while [ -z "$deptno" ]
do
   echo "Enter new deptno value :"
   read deptno || exit 1
done
#
# Modify $$deptno line
#
sed -e 's/^$$deptno=.*/$$deptno='$deptno'/' xyz.txt > xyz.txt.$$
mv xyz.txt.$$ xyz.txt

The 'echo/read' sequence can be replaced by one read statement depending on the shell used.

Code:

# Ksh
   read deptno?"Enter new deptno value : " || exit 1

# Bash
   read -p "Enter new deptno value : " deptno || exit 1

The 'sed/mv' sequence can be replaced by one 'perl' statement

Code:

perl -p -i -e 's/\$\$deptno=.*/\$\$deptno='$deptno'/' xyz.txt

akk8q8 · #3 (**permalink**) 02-23-04, 18:10

perl -p -i -e 's/\$\$deptno=.*/\$\$deptno='$deptno'/' xyz.txt

cud u please explain wht -p -i and -e stand for.

And also while accepting deptno from the user why is it in a while loop?

Thanks
ak

Quote:

Originally posted by akk8q8
Hello,
I am a novice in shell scripting. Need help in modifying the contents of a text file.

the contents of the text file are:
[foldername.session name]
$$deptno=10

I want to change the value $$deptno=40. Cud any one suggest a shell script which prompts the user for the value and updates deptno with the value.

Finally ...the shell script every time its run it sud modify the value of $$deptno as defined by the user.

Thanking you,
ak

akk8q8 · #4 (**permalink**) 02-23-04, 18:12

hello Jean-Pierre,

Cud explain wht p , i, e stand for in the sed command.
Also why do we have to use a while loop for accepting deptno

thanks,
ak

akk8q8 · #5 (**permalink**) 02-23-04, 18:40

The script works perfectly.Thanks

aigles · #6 (**permalink**) 02-24-04, 01:43

Its a 'perl' command (not 'sed').

Quote:

Usage: perl [switches] [--] [programfile] [arguments]
-0[octal] specify record separator (\0, if no argument)
-a autosplit mode with -n or -p (splits $_ into @F)
-c check syntax only (runs BEGIN and END blocks)
-d[:debugger] run scripts under debugger
-D[number/list]set debugging flags (argument is a bit mask or flags)
-e 'command' one line of script. Several -e's allowed. Omit [programfile].
-F/pattern/ split() pattern for autosplit (-a). The //'s are optional.
-i[extension] edit <> files in place (make backup if extension supplied)
-Idirectory specify @INC/#include directory (may be used more than once)
-l[octal] enable line ending processing, specifies line terminator
-[mM][-]module.. executes `use/no module...' before executing your script.
-n assume 'while (<>) { ... }' loop around your script
-p assume loop like -n but print line also like sed
-P run script through C preprocessor before compilation
-s enable some switch parsing for switches after script name
-S look for the script using PATH environment variable
-T turn on tainting checks
-u dump core after parsing script
-U allow unsafe operations
-v print version number, patchlevel plus VERY IMPORTANT perl info
-V[:variable] print perl configuration information
-w TURN WARNINGS ON FOR COMPILATION OF YOUR SCRIPT. Recommended.
-x[directory] strip off text before #!perl line and perhaps cd to directory

The loop ask for deptno until a non null reponse is given.

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