What does '\\K' mean in this regex?

问题:

Given the following shell script, would someone be so kind as to explain the grep -Po regex please?

#!/bin/bash # Issue the request for a bearer token, json is returned raw_json=`curl -s -X POST -d "username=name&password=secret&client_id=security-admin-console" http://localhost:8081/auth/realms/master/tokens/grants/access` # Strip away all but the "access_token" field's value using a Python regular expression bearerToken=`echo $raw_json | grep -Po '"'"access_token"'"\s*:\s*"\K([^"]*)'` echo "The bearer token is:" echo $bearerToken 

So specifically, I'm interested in understanding the parts of the regex

grep -Po '"'"access_token"'"\s*:\s*"\K([^"]*)'` 

and how it works. Why so many quotes? What is the "K" for? I've some experience with grep regex but this confuses me.

This is the actual output of the curl command and the shell script (grep) works as desired returning just the contents of the "access_token" value.

{"access_token":"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.fQmQKn-xatvflHPAaxCfrrVow3ynpw0sREho7__jZo2d0g1SwZV7Lf4C26CcweNLlb3wmKHHo63HRz35qRxJ7BXyiZwHgXokvDJj13yuOb6Sirg9z02n6fwGy8Iog30pUvffnDaVnUWHfVL-h_R4-OZNf-_YUK5RcL2DHt0zUXI","expires_in":60,"refresh_expires_in":1800,"refresh_token":"eyJhbGciOiJSUzI1NiJ9.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.WeiJOC1jQ52aKgnW8UN2Lv9rJ_yKZiOhijOYKLN2EEOkYF8rvRZsSKbTPFKTIUvjnwy2A7V_N-GhhJH4C-T7F5__QPNofSXbCNyvATj52jGLxk9V0Afvk-Z5QAWi55PJRTC0qteeMRcO2Frw-0KtKYe9o3UcGICJubxhZHsXBLA","token_type":"bearer","id_token":"eyJhbGciOiJSUzI1NiJ9.eyJuYW1lIjoiIiwianRpIjoiMGIyMGI0ODctOTI4OS00YTFhLTgyNmMtM2NiOTg0MDJkMzVkIiwiZXhwIjoxNDQ2ODI4MDU5LCJuYmYiOjAsImlhdCI6MTQ0NjgyNzk5OIwouldhaveToBeNutsUiLCJwcmVmZXJyZWRfdXNlcm5hbWUiOiJhZG1pbiIsImVtYWlsX3ZlcmlmaWVkIjpmYWxzZX0.DmG8Lm4niL1djzNrLsZ2CrsB1ZzUPnR2Nm7IZnrwrmkXsrPxjl6pyXKCWSj6pbk2sgVI8NNFqrGIJmEJ7gkTZWm328VGGpJsmMuJBki0KbqBRKORGQSgkas_34rwzhcTE3Iki8h_YVs2vvNIx_eZSOvIzyEcP3IGHuBoxcR6W3E","not-before-policy":0,"session-state":"62efc05c-1bf5-4f55-b749-5e0eff94155b"}

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In case anyone finds this post, this is what I ended up using:

if hash jq 2>/dev/null; then # Use the jq command to safely parse json bearerToken=$(echo $raw_json | jq -r '.access_token') else # Strip away all but the "access_token" field's value using a perl regular expression bearerToken=$(echo $raw_json | grep -Po '"'"access_token"'"\s*:\s*"\K([^"]*)') fi

回答1:

Since not all regex flavors support lookbehind, Perl introduced the \K. In general when you have:

a\Kb 

When “b” is matched, \K tells the engine to pretend that the match attempt started at this position.

In your example, you want to pretend that the match attempt started at what appears after the ""access_token":" text.

This example will better demonstrate the \K usage:

~$ echo 'hello world' | grep -oP 'hello \K(world)' world ~$ echo 'hello world' | grep -oP 'hello (world)' hello world 

文章来源: What does '\\K' mean in this regex?