How to find and replace string without use command Sed?

Question

As we all know, sed is greatly efficient to find and replace string, for example find 'a' and replace it to 'b': sed 's/a/b/g'.

Is it possible to do this with other command or shell script instead of sed?

This is for a cropped linux systems for TV that does not have the sed command. So I have to use other commands or scripts instead of sed 's/a/b/g'. –

Answer 1

The classic alternative for single letter substitutions is the tr command which should be available on just about any system:

$ echo "foobar" | tr a b   
foobbr

tr is better than sed for this actually since using sed (let alone perl or awk) for single letter substitutions is like using a sledge hammer to kill a fly.

grep is not designed for this, it does not modify its input, it only searches through it.

Alternatively, you can use the substitution capabilities of some shells. Here using ksh, zsh or bash syntax:

$ foo="foobar"
$ echo "${foo//a/b}"
foobbr

We could give you more specific answers if you explained exactly what problem you are trying to solve.

Answer 2

Yes there are a variety of ways to do this. You can use awk, perl, or bash to do these activities as well. In general though sed is probably the most apropos tool for doing these types of tasks.

Examples

Say I have this sample data, in a file data.txt:

foo bar 12,300.50
foo bar 2,300.50
abc xyz 1,22,300.50

awk

$ awk '{gsub("foo", "foofoofoo", $0); print}' data.txt 
foofoofoo bar 12,300.50
foofoofoo bar 2,300.50
abc xyz 1,22,300.50

Perl

$ perl -pe "s/foo/foofoofoo/g" data.txt 
foofoofoo bar 12,300.50
foofoofoo bar 2,300.50
abc xyz 1,22,300.50

Inline editing

The above examples can directly modify the files too. The Perl example is trivial. Simply add the -i switch.

$ perl -pie "s/foo/foofoofoo/g" data.txt 

For awk it's a little less direct but just as effective:

$ { rm data.txt && awk '{gsub("foo", "foofoofoo", $0); print}' > data.txt; } < data.txt

This method creates a sub-shell with the braces '{ ... }` where the file is redirected into it via this:

$ { ... } < data.txt

Once the file has been redirected into the sub-shell, it's deleted and then awk is run against the contents of the file that was read into the sub-shells STDIN. This content is then processed by awk and written back out to the same file name that we just deleted, effectively replacing it.

Answer 3

You can use the POSIX tool ex:

ex a.txt <<eof
%s/Sunday/Monday/g
xit
eof

https://pubs.opengroup.org/onlinepubs/9699919799/utilities/ex.html

Answer 4

If you're working with a file rather than a stream, you could use the standard text editor, ed:

printf '%s\n' ',s/a/b/g' w q | ed file.txt

This should be available on any *nix. The comma in ',s/a/b/g' tells ed to work on every line (you can also use %, which will be more familiar if you're used to vim), and the rest of it is a standard search and replace. w tells it to write (save) the file, q tells it to exit.

Note that, unlike sed's -i option (and similar options in other tools), this actually does edit the file in-place rather than cheating with temporary files.

I don't think it's possible to get this working with streams, but then I don't really know much about ed and I wouldn't be surprised if it actually does have that capability (the unix philosophy being what it is).

Answer 5

Using the ancestor ed command (in which -s means quiet (silent) and the comma before the commands means execute on all lines):

Just printing on STDOUT:

ed -s file <<!
,s/a/b/g
,p
q
!

replacing in-place:

ed -s file <<!
,s/a/b/g
w
q
!

Answer 6

If you are using linux OS eg Ubuntu Desktop like me, you will have python installed.

With python, we can do text replacing as below

result=$(python << EOT
s = '$your_string_in_shell_script'
r = s.replace('text to replace', 'replaced by this text')
print(r)
EOT)

echo $result