The replace command is a string-replacement utility. It changes strings in place in files or on the standard input. This command uses a finite state machine to match longer strings first. It can be used to swap strings. This command is similar to the Perl -pie syntax or sed (stream editor) command.
Please note that the replace command is part of is MySQL database system. If you don’t have MySQL installed, you don’t have replace command.
Syntax
replace OLD-STRING NEW-STRING < INPUT-FILE > OUTPUT-FILE |
Examples
To replace all occurrences of word UNIX with Linux, enter:
$ replace UNIX Linux < oldfile > newfile
The replace command can be used in a pipeline, run:
$ cat /etc/passwd | replace : '|'
You can skip the cat command, enter:
$ replace : '|' < /etc/passwd
It also supports few special characters in string replacement:
- \^ : Match start of line.
- $ : Match end of line.
How Do I Update All *.txt Files At Once?
You use bash for loop as follows:
#!/bin/bash for f in /path/to/*.txt do replace UNIX Linux < "$f" > "$f.new" done |
The replace command does not understand regular expression. To use regular expression try the sed command or Perl.
Sed Command Example
To replace all occurrences of word UNIX with Linux using the sed command, enter:
sed 's/UNIX/Linux/g' < input.file > output.file |
OR
sed -i 's/UNIX/Linux/g' input.file |
OR use bash shell for loop as follows to update all *.doc files at once:
#!/bin/bash for f in /path/to/*.doc do sed -i 's/UNIX/Linux/g' "$f" done |
Updated for accuracy!
21 comment
To use perl, just remember Perl Pie!
perl -p -i -e ‘s/hello/goodbye/g’ textfile.txt
Joe, very nice. Your tip sound yummy 🙂 thanks for sharing with us
http://www.debian-administration.org/articles/298 has a fine article and discussion on Perl Pie.
what about this line:
perl -p -i -e ‘s/|00000000.00|/||/g’ myfile.txt
I want to replace |00000000.00| with ||
I get a compilation error.
You need to write it as follows:
perl -p -i -e ‘s/|00000000.00|/||/g’ myfile.txt
|| got some special meaning (regex) | will disable it
This does the trick perfectly! Thanks for sharing this special character technique nixcraft!
or try this…
first make a bash script, ‘fixer.sh’
#!/bin/bash
replace CHANGEFROM CHANGETO $1.tmp
rm $1
mv $1.tmp $1
now run this command line…
$ grep CHANGEFROM |cut -d':' -f1 |xargs -n 1 fixer.sh
the results is that all files in the directory (or whatever you grep for) will be changed automagically.
just make sure the grep doesn’t include the fixer script itself, or it will die half-way through changing when execute permissions are reset!
😉
thanks for sharing this info
Am I the only one who sees no difference in these?
>> perl -p -i -e ’s/|00000000.00|/||/g’ myfile.txt
>> I want to replace |00000000.00| with ||
>> I get a compilation error.
— —
>> You need to write it as follows:
>> perl -p -i -e ’s/|00000000.00|/||/g’ myfile.txt
Cant see the diference… 🙁
find ./* -type f -exec sed -i 's///g' {} ;`replace`
`replace` can work with files, which may be simpler than writing a shell script as mentioned above. It will even convert files in place. Say you want to change an instance of ‘foo’ to ‘bar’ in all files in a certain directory, recursively. In bash,
for i in `grep -lR foo dir/to/files`; do replace foo bar — $i; done
Simply put, use two dashes to separate filenames from the from/to strings, and it’ll convert the files.
I couldn’t even find this command in Ubunto 10.04 (or in repositories). I ended up using rpl instead. Is really fun for databending images.
‘Replace’ is found in mySQL. If you don’t have mySQL, you don’t have `replace`
I want to replace a string in sub directories also(in Linux), is there any specific command for that?
hi,
thanks for the info..nice script. just wanted to add that when i used to ‘for’ loop version w/ ‘sed’ command (in Linux) it would read all the “*.sh” files that i wanted to substitue a string but did not actually make the change. just an fyi, i removed the single quote (‘) in the sed line and it works.
See below:
#!/bin/bash
for f in /path/to/*.doc
do
sed -i s/UNIX/Linux/g “$f”
done
Thanks
for i in `find . -type f`
do
j=`echo $i|sed ‘s/$1/$2/g’`
mv $i $j
done;
I noticed in my bash shell I need to do the following on my Mac:
sed -i ” ‘s/UNIX/Linux/g’ input.file
Otherwise I get stdin error.
Your example below will fail on filenames containing spaces due to the default internal field separator (IFS) breaking on a space character (default=$’ tn’):
To properly handle filenames with spaces, you should set IFS to break on new lines only:
You can also simply run the command in a subshell by enclosing it in parenthesis and not have to worry about resetting IFS at the completion of the loop. Eg.:
However, while replace is a valid solution, I have found sed to be the most robust and much faster than perl for large search and replace tasks.
Thanks!