Replace string in a line, where the line is inputed by a variable

Question

I want to replace a string in a line of a document, with sed. Where the LINE Number value should come from a variable, $var.

I've tried:

sed '%ds/peer/md5/g' $var ./temp.txt

but it gives

sed: -e expression #1, char 1: unknown command: `%'

Also tried:

sed -e '"$var"s/peer/md5/g'-i ./temp.txt
sed: -e expression #1, char 1: unknown command: `"'

Finally tried:

printf '%ds/peer/md5/g;\n' 80 | sed -f - ./temp.txt

which prints correctly, but I can't save the result file with output redirection (>) or -i command.

score 1 · Accepted Answer · answered Jan 23 '20 at 13:59

1

I realized that the correct way is:

sed "$var"'s/string1/string2/' -i ./temp.txt

where var is the variable that have the line number of the file.

answered Jan 23 '20 at 13:59

Hugo Abreu

score 0 · Answer 2 · edited Jan 23 '20 at 14:36

0

Here $ is used for your variable, in sed remember to use " " while using variables within it.

The option -i.bak will create backup file of original.

edited Jan 23 '20 at 14:36

AdminBee

answered Jan 23 '20 at 13:42

Vikram Tidake

1

Hi, the variable must be used to the line number, not the string to be replaced, or replacing string. – Hugo Abreu Jan 23 '20 at 13:56
OOK, you wanted to replace the string in a particular line! – Vikram Tidake Jan 23 '20 at 14:55
1

yes... where the line is given by a variable. – Hugo Abreu Jan 23 '20 at 18:40

2 Answers2