search and replace string using sed

Question

i have a sed command like this for search and replace string inside a file:

sed -i -e 's/`db1`./`db2`./g' result/files1.sql

that is working fine to replace the db1 to db2 inside the file of: result/files1.sql

however when i change it to bash and variable format, it does not work.

sed -i -e "s/`${mydbname}`./`${mydbname2}`./g" "${mypath}"

i get error like:

./mycoolscript: line 241: db1: command not found
./mycoolscript: line 241: db2: command not found

any solution would be great.

Why do you need to add ` around ${mydbname} ? It makes the second sed commands think db1 is a command rather than a string you want to replace. Note that shell will replace any variables including COMMAND inside "" (quote), but will not replace inside '' (single quote). — imapollo
– imapollo, Commented Oct 17, 2013 at 6:46

imapollo · Accepted Answer · 2013-10-17 06:52:33Z

3

If is something you need to replace, you will need to escape by . Here it is

sed -i -e "s/\`${mydbname}\`./\`${mydbname2}\`./g" "${mypath}"

answered Oct 17, 2013 at 6:52

imapollo

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Karan Punamiya · Accepted Answer · 2013-10-17 06:46:21Z

2

Escape the backtick character

sed -i -e "s/\`${mydbname}\`./\`${mydbname2}\`./g" "${mypath}"

Bash treats the part within backticks as a command and first executes that.

answered Oct 17, 2013 at 6:46

Karan Punamiya

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Jotne · Accepted Answer · 2013-10-17 08:05:53Z

0

Try this

sed -i -e "s/${mydbname}/${mydbname2}/g" "${mypath}"

answered Oct 17, 2013 at 8:05

Jotne

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anishsane · Accepted Answer · 2013-10-17 08:41:42Z

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There is one more way, of using single quotes for literals & double quotes only around variables/escape sequences.

sed -i -e 's/`'"${mydbname}"'`./`'"${mydbname2}"'`./g' "${mypath}"

Because of single quotes, you will not have to escape the special characters.

The trade-off between escaping special characters vs. using mix of single & double quotes would depend on number of special characters vs. number of variables.

If there are too many characters that would need escaping & less number of variables, I would prefer mix of single & double quotes.

answered Oct 17, 2013 at 8:41

anishsane

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