Shell Programming and Scripting

Hi greet,

Yeah. Now its working. Thanks a lot. You told me i can edit and save the file with the option -i. Could you please let me know how to do that.

Thanks a lot for your help. Below is the code and output.

Code:

echo "Program Begin" 
for file in *.txt
do
echo "File Name=" $file
sed '1n;$!s/./&a/10' $file
done
echo "Program End"

Output

Code:

Program Begin
File Name= abc.txt
abcdefghij klmnop  qrstuvwxyz
1234567891a0 11 12 13 14 15 16
ABCDEFGHIJaKLMNOPQRSTUVWZYZ
1234567891a0 11 12 13 14 15 16
12345678910 11 12 13 14 15 16
File Name= def.txt
abcdefghij klmnop  qrstuvwxyz
1234567891a0 11 12 13 14 15 16
ABCDEFGHIJaKLMNOPQRSTUVWZYZ
1234567891a0 11 12 13 14 15 16
12345678910 11 12 13 14 15 16
Program End

Good that it works with last change.

to make inplace/infile edit , use

Code:

sed -i '1n;$!s/./&a/10' $file

If you want to save a backup / copy of the file before modifying it, use

Code:

sed -i.bak '1n;$!s/./&a/10' $file

After execution of above command with -i.bak option, you have 2 files now.
1) before modification with .bak extension.
2) Modified file by sed command .

Hi greet,

With option -i, its not working..i get below error.

Code:

$ sh test2.prog
Program Begin
File Name= abc.txt
sed: illegal option -- i
Usage:  sed [-n] [-u] Script [File ...]
        sed [-n] [-u] [-e Script] ... [-f Script_file] ... [File ...]
File Name= def.txt
sed: illegal option -- i
Usage:  sed [-n] [-u] Script [File ...]
        sed [-n] [-u] [-e Script] ... [-f Script_file] ... [File ...]
Program End

Thanks
Bharat

---------- Post updated at 03:34 PM ---------- Previous update was at 03:21 PM ----------

I tried it using another option. and it seems working. Thanks a lo for your help. Below is the code i tried.

Code:

for file in /home/user/bharat/*.RET
do
echo "File Name=" $file

l_fileName=`basename ${file}`_II

mv $file $l_fileName

echo "New File Name=" $file

sed  '1n;$!s/./&I/180' $l_fileName>$file

mv -f $l_fileName /home/user/bharat/archive

done

If we just stick with standard sed addressing constructs and do not depend on non-standard options, you could try something more like:

Code:

#!/bin/ksh
IAm=${0##*/}
tmpf="$IAm.$$"

trap 'rm -f "$tmpf"' EXIT

cd /home/user/bharat
for file in *.RET
do	printf 'File Name=%s\n' "$file"
	sed -e 1n -e '$n' -e 's/./I&/180' "$file" > "$tmpf" && cp "$tmpf" "$file"
done

Note that your description talks about INSERTING a character in the 180th position which I interpret to mean "insert a character before the 180th character on the existing line" while none of your sample input files have 180 characters in any line and all of the samples that have shown examples using character position 10 instead of 180 have been "appending a character after the 10th character" instead of "inserting a character before the 10th character. The above code attempts to "insert a character before the 180th character on lines 2 through n-1, inclusive, for a file that contains n lines.

The code samples you have shown unconditionally move the output produced by sed to the input file whether or not sed succeeded or failed. The above code only modifies the input file if the sed command completes successfully. Furthermore, it copies the updated file back to the original file (which preserves file permissions and hard links) while the moves used by your script will break any hard links to your input files and may destroy the contents of your input file if sed fails for any reason.

Hopefully, this will work better for you.

Note that it is always a good idea to tell us what operating system and shell you're using so the volunteers here trying to help you can avoid suggestions that won't work in your environment.

The previous script was written and tested using a Korn shell, but will work with any shell that is based on Bourne shell syntax and performs parameter expansions required by the POSIX standards (such as ash, bash, dash, ksh, and zsh).

Hi Don,

Thanks for your detailed explanation and solution. I will try this approach and update you.

Thanks
Bharat

Hi Don,

I tested this and works perfectly fine. I have one more requirement with the same operation. If 180th position already have character "I". i do not want to touch that file. I am not getting how to handle that with sed.

Any help is highly appreciated.

Thanks
Bharat

Don't touch that file or line?