Replace string - searching from input file

Shell Programming and Scripting
1

Hi I need help with writing a script to change a string in a file.

The script needs to read an input list (list.txt) file line by line searching for that string in a text.file. Once the string is found the last few words in the string should be replaced.

eg list.txt will contain

hello my name is dave
hello our name is dave

text.file will contain data such as

hello my name is dave
hello mikes name is really dave
hello our name is dave
hello we are dave

once the string is matched it should be changed to :

hello my name is irrelevant now

The text.file should end up as follows if the script has worked:-

hello my name is irrelevant now
hello mikes name is really dave
hello our name is irrelevant now
hello we are dave

I hope i've explained the problem well enough

2

Any attempts from your side?

3

sed '/^hello my name is /s/[^ ]*$/irrelevant now/g' myFile

4

Indeed i've tried to do this using a for loop and sed but not sure if this is the best way of achieving this as i'll need another list for the replacement variable:-

for i in `cat text.file`
do
sed "s/\$i/$var1" text.file > text.file.new
5

sed '/^hello my name is /s/[^ ]*$/irrelevant now/g' myFile
or expanded:

awk -v str='irrelevant now' 'FNR==NR{f1[$0];next} $0 in f1 {$NF=str}1' list.txt text.file
6

Try also

awk  'NR==FNR {T[$0];next} $0 in T {sub (/ [^ ]*$/, " irrelevant now")}1' file1 file2
hello my name is irrelevant now
hello mikes name is really dave
hello our name is irrelevant now
hello we are dave
7

Sorry, but this question reeks like homework so much i have to close it.

@thread-op:

Your solution:

for i in `cat text.file`
do
sed "s/\$i/$var1" text.file > text.file.new

has two shortcomings:

first, the sed-statement is incomplete and should read:

"s/\$i/$var1/"

Notice the "/" at the end. Second, your for-loop is not closed:

for <var> in <list of values>
do
   cmd1
   cmd2
   ...
done

You might want to correct these and then look what your code produces and if it matches what you want. Chances are there are still differences.

Btw., using "for"-loops with open-ended lists (you do not know beforehand how long text.file will be) is never a good idea, though not syntactically wrong. Better replace such constructs with a "while"-loop, which will do the same:

while read <var> ; do
    cmd1 "$VAR"
    cmd2 "$VAR"
    ....
done < /path/to/input.file

I hope this helps.

bakunin