无法找出正则表达式bash或sed或awk

Question

I wanted to split the following jdk-1.6.0_30-fcs.x86_64 to just jdk-1.6.0_30 . I tried the following sed 's/\\([az][^fcs]*\\).*/\\1/' but I end up with jdk-1.6.0_30- . I think am approaching it the wrong way, is there a way to start from the end of the word and traverse backwards till I encounter - ?

Answer 1

Try doing this :

echo 'jdk-1.6.0_30-fcs.x86_64' | sed 's/-fcs.*//'

If using bash , sh or ash , you can do :

var=jdk-1.6.0_30-fcs.x86_64
echo ${var%%-fcs*}
jdk-1.6.0_30

Later solution use parameter expansion , tested on Linux and Minix3

Answer 2

Not exactly, but you can anchor the pattern to the end of the string with $ . Then you just need to make sure that the characters you repeat may not include hyphens:

echo jdk-1.6.0_30-fcs.x86_64 | sed 's/-[^-]*$//'

This will match from a - to the end of the string, but all characters in between must be different from - (so that it does not match for the first hyphen already).

A slightly more detailed explanation. The engine tries to match the literal - first. That will first work at the first - in the string (obviously). Then [^-]* matches as many non- - characters as possible, so it will consume 1.6.0_30 (because the next character is in fact a hyphen). Now the engine will try to match $ , but that does not work because we are not at the end of the string. Some backtracking occurs, but we can ignore that here. In the end the engine will abandon matching the first - and continue through the string. Then the engine will match the literal - with the second - . Now [^-]* will consume fcs.x86_64 . Now we are actually at the end of the string and $ will match, so the full match (which will be removed is) -fcs.x86_64 .

Answer 3

使用cut >>

echo 'jdk-1.6.0_30-fcs.x86_64' | cut -d- -f-2