Replacing first occurence in every line

问题

Supposing I have a document formatted like this:

word1 word2 word3
word4 word5 word6
word7 word8

How do I use sed to replace the first occurence of space with a comma followed by a space so that the document will look like:

word1, word2 word3
word4, word5 word6
word7, word8

Thank you!

回答1:

echo word1 word2 word3|sed -r 's/(\s)/,\1/'

output:

word1, word2 word3

回答2:

Simple:

sed -i 's/ /, /' your_file

This looks for the first occurrence of a space, replaces it with a comma and space, then moves to the next line.

回答3:

how about:

sed -e 's/\s\+/, /'

output:

word1, word2 word3
word4, word5 word6
word7, word8

回答4:

Using awk

awk '{sub(/ /,", ")}1' file
word1, word2 word3
word4, word5 word6
word7, word8

回答5:

sed 's/\([^[:blank:]]\{1,\}\)/\1,/' YourFile

Add a , after first block of "non space", so start of line could be starting with space, it still work and also if line is without work but only with space (no , in this case)

回答6:

echo FRIEND TOO MUCH |sed 's/ /, /'

FRIEND, TOO MUCH

来源：https://stackoverflow.com/questions/20405342/replacing-first-occurence-in-every-line