重击：正则表达式匹配字符的第一次出现

Question

Input:

p45-322-16.jpg

Desired output:

p45

I'm trying to make a bash script with grep or awk or sed or something that could run on a bash shell.

Currently I'm stuck with this:

echo "p45-322-16.jpg" | sed 's/\(.*\)-.*/\1/'

Output:

p45-322

Answer 1

You need to limit what you will accept. Right now, you are accepting too much by using . , and the greedy-by-default nature of regexes is consuming too many characters.

Try either limiting the accepted characters to digits only, or specifically excluding the dash:

\([0-9]*\).*

\([^-]*\).*

Answer 2

echo "p45-322-16.jpg" | sed 's/\([^-]*\).*/\1/'

The .* part of your regex is greedy, so it reads as far as possible so that the regex still matches. This means it claims everything up to the last - .

Use [^-]* to match everything until a - .

Answer 3

You can use cut command: echo "p45-322-16.jpg" | cut -d"-" -f1 echo "p45-322-16.jpg" | cut -d"-" -f1