I have file which contains text at line 30 which is:
Icon="\<some path which we do not know\icon.png"
I want to replace above with:
Icon="\home\user\Img\Icons\icon.png"
What is the best way to do it.?
Thanks.
Best way:
perl -pi -e 's/\\<some path which we do not know/\\home\\user\\Img\\Icons/' text.txt
Perl approach is more preferred than sed, because of Unix compatibility.
You can either use an editor to do this manually or if you prefer to do it non interactively, you can use a small shell pipeline and sed.
sed `3 s/big path/custom path/` input_file.txt
where 3 is the line number, big path is what you want to replace and custom path is what you to want to replace it with. input_file.txt is your input file. This will print the replaced file onto the screen which you can redirect into another file using the > operator.
As a concrete example, suppose I have this file (input_file.txt)
Header
Random test
/bad/path/to/some/directory/icon.png
/bad/path/to/some/directory/icon.png
Footer
Now I'm going to run my command like so.
cat input_file.txt | sed '4 s/\/bad\/path\/to\/some\/directory\//\/home\/noufal\//'
and I get
Header
Random test
/bad/path/to/some/directory/icon.png
/home/noufal/icon.png
Footer
Notice that it has changed only the 4th line. The extra \ characters in the command are to escape the / character which has special meaning for sed.
you can use vim to find and replace your strings http://vim.wikia.com/wiki/Search_and_replace or use 'sed' command
Related
I have got a csv file like this:
120,256,300
36,255,12
etc...
I want to add a fixed string like 'USA' to all lines in order to obtain:
120,256,300,USA
36,255,12,USA
etc...
How can I do that?
Thanks
From a text processing point of view that CSV file is plain text in this context, you just want to attach , USA to each line.
The easiest (and operationally least expensive) way to do so is probably:
sed -i '' 's/$/, USA/' file
What this does is to instruct sed to look for the end of line $ and "replace" it with , USA. As sed is line-based this obviously doesn't actually trim out the new line of the file.
-i '' instructs sed to make the changes in-line without creating a backup file.
If you wanted a backup you can put the desired extension instead of '', e.g. -i .bak.
You can just use sed: cat <input-file> | sed 's/\(.*\)/\1, USA/'.
Here s is the substitute command, which uses the following character as a separator between a regular expression and a substitution. For the regular expression, the escaped parenthesis are used to create a capture group, the regex .* captures the entire line. For the substitution, the \1 inserts the first capture group, and then the , USA text is appended.
You can perform the replacement in place using: sed -i .bak 's/\(.*\)/\1, USA/' <input-file>
I am trying to replace a specific line in a txt file with my shell script, for example;
cat aa.txt:
auditd=0
bladeServerSlot=0
When I run my script I would like to change "bladeServerSlot" to 12 as following;
cat aa.txt:
auditd=0
bladeServerSlot=12
Could you please help me?
Using sed and backreferencing:
sed -r '/bladeServerSlot/ s/(^.*)(=.*)/\1=12/g' inputfile
Using awk , this will search for the line which contains bladeServerSlot and replace the second column of that line.
awk 'BEGIN{FS=OFS="="}/bladeServerSlot/{$2=12}1' inputfile
perl -pe 's/bladeServerSlot=\K\d+/12/' aa.txt > output.txt
The \K is a particular form of the positive lookbehind, which discards all previous matches. So we need to replace only what follows. The s/ is applied by default to $_, which contains the current line. The -p prints $_ for every line, so all other lines are copied. We redirect output to a file.
Is it really necessary to replace the line in your example? As bladeServerSlot is a variable you could reset the value.
bladeServerSlot=`any command`
Or you could just let this variable be filled by a Parameter provided to this script.
bladeServerSlot=$1
With $1being the first parameter of your script. I think this would be the cleaner way do solve your issue than to do fancy regex here. The sed/perl solutions will work, but they are not very clear to other people reading your script.
I am trying to replace a line in a file with multiple lines. When I had only one new line char ( \'$'\n ). it worked fine, however when I use two of them, it escapes my sed and the file wont run anymore.
sed 's/TextImLookingFor/My\'$'\nReplacement\'$'\nText/g' /path/to/File.txt
File.txt:
This is a file
TextImLookingFor
look at all this text
DesiredOutput
This is a file
My
Replacement
Text
look at all this text
Actual Output
unexpected EOF while looking for matching ''''
syntax error: unexpected end of file
Using older BSD sed you can do:
sed $'s/TextImLookingFor/My\\\nReplacement\\\nText/' file
This is a file
My
Replacement
Text
look at all this text
This should work with newer gnu-sed as well. However newer gnu-sed may just need:
sed 's/TextImLookingFor/My\nReplacement\nText/' file
This might work for you (GNU sed):
sed '/TextImLookingFor/c\My\nReplacement\nText' file
The problem with this command
sed 's/TextImLookingFor/My\'$'\nReplacement\'$'\nText/g' /path/to/File.txt
is that it isn't parsing the way you expect it is.
You cannot escape a single quote inside a single quoted string. You can escape a single quote inside a $'...' quoted string however (I'm not really sure why).
So the above command does not parse this way (as you might expect):
[sed] [s/TextImLookingFor/My\'$[\nReplacement\'$]\nText/g] [/path/to/File.txt]
instead it parses this way:
[sed] [s/TextImLookingFor/My\]$[\nReplacement\'$]\nText/g' [/path/to/File.txt]
with a mismatched single quote at the end and an unquoted \nText/g bit.
That is the cause of your problem.
If you can't just use \n in your replacement (your version of sed doesn't support that) and you need to use $'\n' then you would need to use something like
sed 's/TextImLookingFor/My\'$'\nReplacement\\'$'\nText/g' /path/to/File.txt
I need to read a file line by line in Linux, find a substring in each line, remove it and place it at the end of that line.
Example:
Line in the original file:
a,b,c,substring,d,e,f
Line in the output file:
a,b,c,d,e,f,substring
How do I do it with the Linux command? Thanks!
sed '/substring/{ s///; s/$/substring/;} '
will handle a fixed substring. Note that if substring begins with a ,, this handles your example case well. If the substring is not fixed but may be a general regular expression:
sed 's/\(substring\)\(.*\)/\2\1'
If you are looking for general csv parsing, you should rephrase the question. (It will be difficult to apply this solution to find a fixed string at the start of a line if you are thinking of the input as comma separated fields.)
I always prefer to use perl's command line to do such regex tasks - perl is powerful enough to cover awk and sed in most of my usages, and both available in windows and linux, it is just easy and handy to me, so the solution in perl would be like:
perl -ne "s/^(.*?)(?:(?<comma>,)(?<substr>substring)|(?<substr>substring)(?<comma>,))(?<right>.*)$/$1$+{right}$+{comma}$+{substr}/; print" input.txt > output.txt
or a simpler one:
perl -lpe "if(s/(,substring|substring,)//){ s/$/,substring/ }" input.txt > output.txt
input.txt
substring,a,b,c,d,e,f
a,b,c,substring,d,e,f
a,b,c,d,e,f,substring
substring,a
a,substring
substring
a
output.txt
a,b,c,d,e,f,substring
a,b,c,d,e,f,substring
a,b,c,d,e,f,substring
a,substring
a,substring
substring
a
You can edit based on your actual input:
If there are any space between words and commas
If you are using tab as separator
Some explanation of the command line:
use perl's -n -e options: -n means process the input line by line in a loop; -e means one line program in the command line
use perl's -l -p options: -l means process multilines; -p means always print
The one line program is just a regex replacement and a print
(?:pattern) means group but don't capture the match
(?<comma>) is a named group, you then need to use $+{comma} hash to access it
I have a huge SQL file that gets executed on the server. The dump is from my machine and in it there are a few settings relating to my machine. So basically, I want every occurance of "c://temp" to be replace by "//home//some//blah"
How can this be done from the command line?
sed is a good choice for large files.
sed -i.bak -e 's%C://temp%//home//some//blah%' large_file.sql
It is a good choice because doesn't read the whole file at once to change it. Quoting the manual:
A stream editor is used to perform
basic text transformations on an input
stream (a file or input from a
pipeline). While in some ways similar
to an editor which permits scripted
edits (such as ed), sed works by
making only one pass over the
input(s), and is consequently more
efficient. But it is sed's ability to
filter text in a pipeline which
particularly distinguishes it from
other types of editors.
The relevant manual section is here. A small explanation follows
-i.bak enables in place editing leaving a backup copy with .bak extension
s%foo%bar% uses s, the substitution command, which
substitutes matches of first string
in between the % sign, 'foo', for the second
string, 'bar'. It's usually written as s//
but because your strings have plenty
of slashes, it's more convenient to
change them for something else so you
avoid having to escape them.
Example
vinko#mithril:~$ sed -i.bak -e 's%C://temp%//home//some//blah%' a.txt
vinko#mithril:~$ more a.txt
//home//some//blah
D://temp
//home//some//blah
D://temp
vinko#mithril:~$ more a.txt.bak
C://temp
D://temp
C://temp
D://temp
Just for completeness. In place replacement using perl.
perl -i -p -e 's{c://temp}{//home//some//blah}g' mysql.dmp
No backslash escapes required either. ;)
Try sed? Something like:
sed 's/c:\/\/temp/\/\/home\/\/some\/\/blah/' mydump.sql > fixeddump.sql
Escaping all those slashes makes this look horrible though, here's a simpler example which changes foo to bar.
sed 's/foo/bar/' mydump.sql > fixeddump.sql
As others have noted, you can choose your own delimiter, which would prevent the leaning toothpick syndrome in this case:
sed 's|c://temp\\|home//some//blah|' mydump.sql > fixeddump.sql
The clever thing about sed is that it operating on a stream rather than a file all at once, so you can process huge files using only a modest amount of memory.
There's also a non-standard UNIX utility, rpl, which does the exact same thing that the sed examples do; however, I'm not sure whether rpl operates streamwise, so sed may be the better option here.
The sed command can do that.
Rather than escaping the slashes, you can choose a different delimiter (_ in this case):
sed -e 's_c://temp/_/home//some//blah/_' file1.txt > file2.txt
perl -pi -e 's#c://temp#//home//some//blah#g' yourfilename
The -p will treat this script as a loop, it will read the specified file line by line running the regex search and replace.
-i This flag should be used in conjunction with the -p flag. This commands Perl to edit the file in place.
-e Just means execute this perl code.
Good luck
gawk
awk '{gsub("c://temp","//home//some//blah")}1' file