How to use grep to get anything just after `name=`?
RegexBashGrepRegex Problem Overview
I’m stuck in trying to grep anything just after name=
, include only spaces and alphanumeric.
e.g.:
name=some value here
I get
some value here
I’m totally newb in this, the following grep match everything including the name=
.
grep 'name=.*' filename
Any help is much appreciated.
Regex Solutions
Solution 1 - Regex
As detailed here, you want a positive lookbehind clause, such as:
grep -P '(?<=name=)[ A-Za-z0-9]*' filename
The -P makes grep use the Perl dialect, otherwise you'd probably need to escape the parentheses. You can also, as noted elsewhere, append the -o
parameter to print out only what is matched. The part in brackets specifies that you want alphanumerics and spaces.
The advantage of using a positive lookbehind clause is that the "name=" text is not part of the match. If grep highlights matched text, it will only highlight the alphanumeric (and spaces) part. The -o parameter will also not display the "name=" part. And, if you transition this to another program like sed that might capture the text and do something with it, you won't be capturing the "name=" part, although you can also do that by using capturing parenthess.
Solution 2 - Regex
Try this:
sed -n 's/^name=//p' filename
It tells sed to print nothing (-n) by default, substitute your prefix with nothing, and print if the substitution occurs.
Bonus: if you really need it to only match entries with only spaces and alphanumerics, you can do that too:
sed -n 's/^name=\([ 0-9a-zA-Z]*$\)/\1/p' filename
Here we've added a pattern to match spaces and alphanumerics only until the end of the line ($), and if we match we substitute the group in parentheses and print.
Solution 3 - Regex
grep does not extract like you expect. What you need is
grep "name=" file.txt | cut -d'=' -f1-
Solution 4 - Regex
gawk
echo "name=some value here" | awk -F"=" '/name=/ { print $2}'
or with bash
str="name=some value here"
IFS="="
set -- $str
echo $1
unset IFS
or
str="name=some value here"
str=${str/name=/}
Solution 5 - Regex
grep will print the entire line where it matches the pattern. To print only the pattern matched, use the grep -o option. You'll probably also need to use sed to remove the name= part of the pattern.
grep -o 'name=[0-9a-zA-Z ]' myfile | sed /^name=/d