[SOLVED] Why is sed with 'g' modifier not replacing all matches

Issue

sed with 'g' modifier not replacing all matches.

Example:

$ sed -e 's:foo\([^\s]*\):\1 :g' <(echo "hey foobar foobar ")

Expected:

"hey bar bar"

Actual:

"hey bar foobar"

What am I missing here?

Solution

\s is a PCRE extension that POSIX sed isn't guaranteed to implement; and without it being honored, your match stops only at the letter s or at backslashes, not at spaces.

You get correct behavior if instead you use:

sed -re 's:foo([^[:space:]]*):\1 :g'

...or...

sed -e 's:foo\([^[:space:]]*\):\1 :g'

---

To better see what's going on for your self, you can change the replacement string to have sigils around it, to see exactly what is being captured:

$ sed -e 's:foo\([^\s]*\):<\1 >:g' <<<"hey foobar foobar "
hey <bar foobar  >
$ sed -e 's:foo\([^\s]*\):<\1 >:g' <<<"hey foobar foobar s foobar foobar "
hey <bar foobar  >s <bar foobar  >

Answered By - Charles Duffy

Answer Checked By - Mildred Charles (WPSolving Admin)