Replacing a string by a file using Sed

Question

Lets say i have two files foo and bar. I want a replace the string "this is test" in foo with the contents of the file bar. How can i do this using a one liner sed?

I have used:

sed -i.bak 's/this is test/$(cat bar)\n/g' foo

but the the string is being replaced by literal $(cat bar) rather than the contents of bar. I have tried using quotations but the result remains the same.

Radu's answer is correct as far as the quote is concerned. Now the problem is lets say my bar file contains:

this
is
a
test
file

Now if i run the command it gives an error:

sed: -e expression #1, char 9: unterminated `s' command

18 times.

does the contents of the file bar contains newline characters? — Avinash Raj, Oct 23 '14 at 10:58
Does it have to be sed? To avoid escaping issues, I'd rather use another scripting language that is better suited for file interaction like Awk, Python, Perl, Ruby, or whatnot. — David Foerster, Oct 23 '14 at 13:13
I was trying to check this using sed. So it would be great if a solution is available in Sed. — heemayl, Oct 23 '14 at 13:16
If you mean "this is test" is a separate line then solution is using sed $'/this is test/ {r bar\n d}' foo .otherwise if "this is test" is a string in a line then solution is using X=$(echo $(cat bar));sed "s/this is test/$X/" foo. — αғsнιη, Oct 23 '14 at 13:22
Got it. Now what if i want the start of the file foo i.e. ^ is to be replaced by the file bar? — heemayl, Oct 23 '14 at 13:28
Actually i got my answer but this is just an extension to check if any tweaking can be done further. — heemayl, Oct 23 '14 at 14:08

score 10 · Accepted Answer · edited Apr 13 '17 at 12:37

10

The following command should work for what you want:

sed "s/this is test/$(cat bar)/" foo

If foo contain more then one line, then you can use:

sed "s/this is test/$(sed -e 's/[\&/]/\\&/g' -e 's/$/\\n/' bar | tr -d '\n')/" foo

or:

sed -e '/this is a test/{r bar' -e 'd}' foo

Source of the last two commands: Substitute pattern within a file with the content of other file

To make the change in foo file, use sed -i.

edited Apr 13 '17 at 12:37

Community

1

answered Oct 23 '14 at 11:07

Radu Rădeanu

169,590

1

it's not working for me.. – Avinash Raj Oct 23 '14 at 11:11
@Radu: Please check my edits. I have tried this already. – heemayl Oct 23 '14 at 11:12
@heemayl you used the wrong quotes. – muru Oct 23 '14 at 11:20
@heemayl No, you tried using simple quotes, in my answer I used double quotes. See Difference between single and double quotes in bash. *Single quotes won't interpolate anything, but double quotes will (for example variables, backticks, certain \ escapes, etc...)* – Radu Rădeanu Oct 23 '14 at 11:21
@RaduRădeanu: Yes, I got it. please check my edits for problem regarding new lines. – heemayl Oct 23 '14 at 11:35
@AvinashRaj There is a solution for this also... – Radu Rădeanu Oct 23 '14 at 11:49
@heemayl Check my new edits – Radu Rădeanu Oct 23 '14 at 11:50
1

I don't know if your answer is correct since the OP's question said replace the string "this is test" and not replace the line "this is test". If the line is "this is test in foo file" in foo file, then you deleted "in foo file" string at the end of that line(in your second command). but he/she marked as answer then I think the "this is test" is in a separate line not string into line but again title says that is STRING. – αғsнιη Oct 23 '14 at 12:42
@KasiyA: I meant line in this case but what if i want to replace the start of first line of foo with content of file bar? – heemayl Oct 23 '14 at 12:49

Guru · Answer 2 · 2014-10-23T11:48:39.973

7

One way:

sed -e '/this is test/r bar' -e '/this is test/d' foo

Sample result:

$ cat bar
12
23
$ cat foo
ab
this is test
cd
this is test
ef
$  sed -e '/this is test/r bar' -e '/this is test/d' foo
ab
12
23
cd
12
23
ef

edited Oct 23 '14 at 11:48

answered Oct 23 '14 at 11:34

Guru

729

Not working in my case. – heemayl Oct 23 '14 at 11:44
"Not working" means error or result not as expected or something else? – Guru Oct 23 '14 at 11:45
Same mentioned error i.e. sed: -e expression #1, char 9: unterminated `s' command – heemayl Oct 23 '14 at 11:46
Can you tell me please what /r is doing here? – heemayl Oct 23 '14 at 12:07
@heemayl r - append file to stdout after flush. See http://unix.stackexchange.com/a/26290/37944 – Radu Rădeanu Oct 23 '14 at 12:10
@heemayl please check that you have typed @Guru's answer exactly as shown - it does not use an s command – steeldriver Oct 23 '14 at 12:12
It was my mistake. +1. If i want to replace the start of first line of foo with bar what will be the modification? – heemayl Oct 23 '14 at 12:27
And also you have this problem too. – αғsнιη Oct 23 '14 at 12:44

score 1 · Answer 3 · answered Sep 19 '19 at 13:51

1

When you need to replace an entire line with the contents of a file, you can use r to insert a file and d to delete the current line:

sed -e "/regex/{r/path/to/file" -e "d}"

answered Sep 19 '19 at 13:51

aleb

136

Replacing a string by a file using Sed

3 Answers3

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