Replace a string in shell script using a variable

unix shell sed
Vijay picture Vijay · Jul 22, 2010 · Viewed 439.2k times · Source

I am using the below code for replacing a string inside a shell script.

echo $LINE | sed -e 's/12345678/"$replace"/g'

but it's getting replaced with $replace instead of the value of that variable.

Could anybody tell what went wrong?

Answer

paxdiablo picture paxdiablo · Jul 22, 2010

If you want to interpret $replace, you should not use single quotes since they prevent variable substitution.

Try:

echo $LINE | sed -e "s/12345678/\"${replace}\"/g"

assuming you want the quotes put in. If you don't want the quotes, use:

echo $LINE | sed -e "s/12345678/${replace}/g"

Transcript:

pax> export replace=987654321
pax> echo X123456789X | sed "s/123456789/${replace}/"
X987654321X
pax> _

Just be careful to ensure that ${replace} doesn't have any characters of significance to sed (like / for instance) since it will cause confusion unless escaped. But if, as you say, you're replacing one number with another, that shouldn't be a problem.

Related questions

Find and replace in file and overwrite file doesn't work, it empties the file

I would like to run a find and replace on an HTML file through the command line. My command looks something like this: sed -e s/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g index.html > index.html When …

Read More
Bash tool to get nth line from a file

Is there a "canonical" way of doing that? I've been using head -n | tail -1 which does the trick, but I've been wondering if there's a Bash tool that specifically extracts a line (or a range of lines) from a …

Read More
Shell script - remove first and last quote (") from a variable

Below is the snippet of a shell script from a larger script. It removes the quotes from the string that is held by a variable. I am doing it using sed, but is it efficient? If not, then what is …

Read More