Extract email string from string in bash - string

Question

I have a variable: $change.
I have tried to extract email from it (find the string between "by" and "#"):
change="Change 1234 on 2016/08/31 by name#company.com 'cdex abcd'"
email=$(echo $change|sed -e 's/\by\(.*\)#/\1/')
It did not work.

Answer 1

You have an escape character before b, which makes it \b. And this is a word boundary, so something you don't want here.
See the difference:
$ echo "$change" | sed -e 's/\by\(.*\)#/\1/'
# ^
Change 1234 on 2016/08/31 by name#company.com 'cdex abcd'
$ echo "$change" | sed -e 's/by\(.*\)#/\1/'
# ^
Change 1234 on 2016/08/31 namecompany.com 'cdex abcd'
# ^
# by is not here any more
But if you want to get the name, just use .* to match everything up to by:
$ echo "$change" | sed -e 's/.*by\(.*\)#/\1/'
namecompany.com 'cdex abcd'
Finally, if what you want is just the data between by (note the trailing space) and #, use either of these (with -r you don't have to escape the captured groups):
sed -e 's/.*by \(.*\)#.*/\1/'
sed -r 's/.*by (.*)#.*/\1/'
With your input:
$ sed -e 's/.*by \(.*\)#.*/\1/' <<< "Change 1234 on 2016/08/31 by name#company.com 'cdex abcd'"
name

Answer 2

Using grep -oP you can use match reset \K:
grep -oP ' by \K[^#]*' <<< "$change"
name
or using lookbehind:
grep -oP '(?<= by )[^#]*' <<< "$change"
name

Answer 3

There is no need to resort sed, awk, grep, etc. use regular expression matching:
[[ $change =~ by\ ([^#]*)# ]] && email=${BASH_REMATCH[1]}
From the man page
An additional binary operator, =~, is available, with the same
precedence as == and !=. When it is used, the string to the
right of the operator is considered an extended regular expres-
sion and matched accordingly (as in regex(3)). The return value
is 0 if the string matches the pattern, and 1 otherwise. If the
regular expression is syntactically incorrect, the conditional
expression's return value is 2. If the shell option nocasematch
is enabled, the match is performed without regard to the case of
alphabetic characters. Any part of the pattern may be quoted to
force the quoted portion to be matched as a string. Bracket
expressions in regular expressions must be treated carefully,
since normal quoting characters lose their meanings between
brackets. If the pattern is stored in a shell variable, quoting
the variable expansion forces the entire pattern to be matched
as a string. Substrings matched by parenthesized subexpressions
within the regular expression are saved in the array variable
BASH_REMATCH. The element of BASH_REMATCH with index 0 is the
portion of the string matching the entire regular expression.
The element of BASH_REMATCH with index n is the portion of the
string matching the nth parenthesized subexpression.
It might be surprising, that the pattern is written without surrounding quotes, which is why it is probably a good idea to use a variable for the pattern instead:
regex='by ([^#]*)#'
[[ $change =~ $regex ]] && email=${BASH_REMATCH[1]}

Answer 4

With sed:
sed -E 's/.* by ([^#]+).*/\1/' <<<"$change"
With awk:
awk -F# '{sub(".* ", "", $1); print $1}' <<<"$change"
Example:
$ sed -E 's/.* by ([^#]+).*/\1/' <<<"Change 1234 on 2016/08/31 by name#company.com 'cdex abcd'"
name
$ awk -F# '{sub(".* ", "", $1); print $1}' <<<"Change 1234 on 2016/08/31 by name#company.com 'cdex abcd'"
name

Answer 5

awk version, this will use awk's inbuilt split function to split 6th field using "#" as delimiter and store it in an array named a. Print it for printing first value of array a.
echo $change |awk '{ split($6,a,"#"); print a[1]}'
name
In case you need complete email address then :
echo $change |awk '{print $6}'
name#company.com

Answer 6

Solution with Parameter Expansion
First, a temporary variable that deletes string upto by and a space
$ change="Change 1234 on 2016/08/31 by name#company.com 'cdex abcd'"
$ tmp="${change#*by }"
$ echo "$tmp"
name#company.com 'cdex abcd'
Then, extract either the string before #
$ email="${tmp%#*}"
$ echo "$email"
name
Or, extract complete email address
$ email="${tmp%% *}"
$ echo "$email"
name#company.com
Edit:
To extract multiple strings separated by comma:
$ change="Change 1234 on 2016/08/31 by name#company.com 'cdex abcd'"
$ email=$(echo "$change" | perl -ne 'print join(",",/(\S+)#/g)')
$ echo "$email"
name
$ change="by name#company.com asd abcd#xyz.net 123 tom#xyz asdf"
$ email=$(echo "$change" | perl -ne 'print join(",",/(\S+)#/g)')
$ echo "$email"
name,abcd,tom