I want to add hashes to all the lines in a regular text file. I'm fine with both the use of terminal and GUI—I just need to get it done.
8 Answers
You can use sed
to do that:
sed -i.bak 's/^/##/' file
This replaces the start of the line (^
) with ##
.
With the -i.bak
switch, sed
edits the file in-place, but creates a backup copy with extension.bak
.
-
1+1 This is the first time I encounter this backup method. I always did an inline replace directly:
sed 's/^/##/' -i file
. In this case, this would be preferred since it cannot go wrong. In other cases, this command can be combined withdiff -u file.bak file
to see the differences (if necessary, pipe it throughless
). If it's confirmed to work, the backup can be removed. Otherwise it could be restored with a simplemv file.bak file
. Jul 30, 2011 at 8:28 -
1Elegant. I was thinking about something like
sed 's/^\(.*\)$/##\1/'
, but this is much nicer.– arrangeJul 31, 2011 at 8:54 -
-
Here is a solution to this problem using perl
perl -e 'while (<>) {print "##$_"}' < infile > outfile
-
2The
-p
switch is also useful:perl -pe 's/^/##/' infile > outfile
. (There's also the-i[extension]
switch for replacing the target file in-place.) perldoc.perl.org/perlrun.html#%2a-p%2a Jul 31, 2011 at 7:51
While we are at it:
gawk -i inplace '{print "##"$0}' infile
This uses the (comparatively new) inplace editing plugin for GNU awk 4.1.0+.
Here's a bash
way:
while read -r; do printf '##%s\n' "$REPLY"; done < infile > outfile
(In the bash
shell, running read -r
with no other arguments works like IFS= read -r REPLY
.)
This is stylistically inspired by beav_35's perl solution, which I admit probably runs much faster for huge files, since perl
may be expected to be more efficient than a shell when it comes to text processing.
sed -i
is not POSIX-standard, so if you are a purist you will want to use ed
:
printf ",s/^/##/\nw\nq" | ed -s file.txt
Here's an easier perl
way than presented elsewhere:
perl -pi -e 'print "##"' YOURFILEHERE
This (ab)uses the fact that perl -p
prints the line after executing the command given in -e
.
You can use Vim in Ex mode:
ex -sc '%s/^/##/|x' file
%
select all liness
substitutex
save and close
Can be done with python's mapping function and redirecting stdin:
$ cat input.txt
lorem ipsum
quick brown fox
hello world
$ python -c 'import sys;print "".join(map(lambda x: "##"+x,sys.stdin.readlines()))' < input.txt
##lorem ipsum
##quick brown fox
##hello world
Save the output to new file and use it instead of original