Replace the string which has a pattern like using sed

Question

How to use like (.*) operation in sed to search a pattern (eg: STRING.*) and append "*" to the end of the string that matches.

Below is the example:

cat file1.txt 
MAC BOOK
MODERN MACHINE
MECHANICS
MOUNT
DISK
DATA INFORMATICS

cat file2.txt 
MAC
DATA

for line in $(cat file2.txt|uniq)
do
    sed -i "/$line.*/s/$line.*/$line.**/" file1.txt
done

Expected output:

cat file1.txt

MAC* BOOK
MODERN MACHINE*
MECHANICS
MOUNT
DISK
DATA* INFORMATICS

Answer 1

A one-liner:

$ sed -r '/'"$(paste -sd'|' file2.txt)"'/s/$/*/' file1.txt
MAC*
MACHINE*
MECHANICS
MOUNT
DISK
DATA*

The paste command creates a regular expression from file2:

$ paste -sd'|' file2.txt
MAC|DATA

Then the sed command looks file lines matching this regex, and replaces the end-of-line with an asterisk.

Add -i to the sed command to complete the task.

---

Update for your new input:

awk -v patt="$(paste -sd'|' file2.txt)" '{ 
    for (i=1; i<=NF; i++)
       if ($i ~ patt)
           $i = $i "*"
    print
}' file1.txt

MAC* BOOK
MODERN MACHINE*
MECHANICS
MOUNT
DISK
DATA* INFORMATICS

and to edit save the output back into the file:

tmp=$(mktemp)
awk ... file1.txt > "$tmp" && mv "$tmp" file1.txt

Or, with the latest GNU awk:

gawk -i inplace -v patt="$(paste -sd'|' file2.txt)" '{ 
    for (i=1; i<=NF; i++)
       if ($i ~ patt)
           $i = $i "*"
    print
}' file1.txt

Answer 2

You can just replace the "end of line" with * when you match like:

for line in $(uniq file2.txt); do
    sed -i "/$line/s/\$/*/" file1.txt
done

though this will only work with GNU sed, and it will match $line anywhere in the line, so hopefully that's what you expect

Answer 3

awk is better suited for this:

awk 'FNR==NR{a[$1];next} {for (i in a) if (index($1, i)) $0 = $0 "*"}1' file2.txt file1.txt
MAC*
MACHINE*
MECHANICS
MOUNT
DISK
DATA*

Answer 4

I think what you are looking for is this:

for line in $(cat file2.txt|uniq)
do
    sed -i "s/\(${line}.*\)/\1\*/" file1.txt
done

You can use () in the sed search to save the result and \\1 to use it in the replacement.