How to replace a particular string with another in UNIX shell script

Question

Could you please let me know how to replace a particular string present in a text file or ksh file in the server with another string ?

For example :-

I have 10 files present in the path /file_sys/file in which i have to replace the word "BILL" to "BILLING" in all the 10 files.

Answer 1

Works for me:

I created a file 'test' with this content: "This is a simple test". Now I execute this call to the sed command:

sed -i 's/ is / is not /' test

Afterwards the file 'test' contains this content: "This is not a simple test"

---

If your sed utility does not support the -i flag, then there is a somewhat awkward workaround:

sed 's/ is / is not /' test > tmp_test && mv tmp_test test

Answer 2

This should work. Please find the testing as well.

$ cat > file1

I am a BILL boy

sed 's/[[:alnum:]   [:cntrl:]   [:lower:]   [:space:]   [:alpha:]   [:digit:]   [:print:]   [:upper:]   [:blank:]   [:graph:]   [:punct:]   [:xdigit:]]BILL[[:alnum:]   [:cntrl:]   [:lower:]   [:space:]   [:alpha:]   [:digit:]   [:print:]   [:upper:]   [:blank:]   [:graph:]   [:punct:]   [:xdigit:]]/BILLING/g' file1>file2

$ cat file2

I am a BILLING boy

Answer 3

Using sed:

sed 's/\bBILL\b/BILLING/g' file

For inplace:

sed --in-place 's/\bBILL\b/BILLING/g' file

Answer 4

A little for loop might assist for dealing with multiple files, and here I'm assuming -i option is not available:

for file in $(grep -wl BILL /file_sys/file/*); do
    echo $file
    sed -e 's/\bBILL\b/BILLING/g' $file > tmp
    mv tmp $file
done

Here's what's happening:
  grep -w          Search for all (and only) files with the word BILL
  grep -l          Listing the file names (rather than content)
  $(....)          Execute whats inside the brackets (command substitution)
  for file in   Loop over each item in the list (each file with BILL in it)
  echo $file     Print each file name we loop over
  sed command   Replace the word BILL (here, specifically delimited with word boundaries "\b") with BILLING, into a tmp file
  mv command     Move the tmp file back to the original name (replace original)

You can easily test this without actually changing anything - e.g. just print the file name, or just print the contents (to make sure you've got what you expect before replacing the original files).