Regex to match characters between two specific characters in shell script-CodePudding

I want to clean my file before/after saving so I have to delete unnecessary characters that I have there. Sadly, even that my regex is working in Regex101, it does not work in shell script I wrote.

I am getting my list from Kubernetes via

kubectl get pods -n $1 -o jsonpath='{range .items[*]}{@.spec.containers[*].image}{","}{@.status.containerStatuses[*].imageID}{"\n"}{end}'

Then I saving it to the temp file and using sed to clear it - the regex should match and (sed should) delete any character between , and @ (also should delete @). I am escaping them since they are special characters.

sed -i 's/(?<=\,)(.*?)(?<=\@)//g' temp

The problem is that this regex is working fine (for example in Regex101) but is not working with the sed command. I even tried awk but getting the same output.

awk '!/(?<=\,)(.*?)(?<=\@)/' temp

Am I missing something or is the regex acting differently somehow in Unix/shell?

Thanks for any input.

Example content of the file (for test):

docker.elastic.co/elasticsearch/elasticsearch:7.17.5,docker-pullable://docker.elastic.co/elasticsearch/elasticsearch@sha256:76344d5f89b13147743db0487eb76b03a7f9f0cd55abe8ab887069711f2ee27d
docker.io/bitnami/kafka:3.3.1-debian-11-r11,docker-pullable://bitnami/kafka@sha256:be29db0e37b6ab13df5fc14988a4aa64ee772c7f28b4b57898015cf7435ff662
docker.io/bitnami/mongodb:6.0.3-debian-11-r0,docker-pullable://bitnami/mongodb@sha256:e7438d7964481c0bcfcc8f31bca2d73022c0b7ba883143091a71ae01be6d9edb
docker.io/bitnami/postgresql:14.1.0-debian-10-r80,docker-pullable://bitnami/postgresql@sha256:6eb9c4ab3444e395df159e2cad21f283e4bf30802958467590c886f376dc9959
docker.io/bitnami/zookeeper:3.8.0-debian-11-r47,docker-pullable://bitnami/zookeeper@sha256:0f3169499c5ee02386c3cb262b2a0d3728998d9f0a94130a8161e389f61d1462

Expected output:

docker.elastic.co/elasticsearch/elasticsearch:7.17.5,sha256:76344d5f89b13147743db0487eb76b03a7f9f0cd55abe8ab887069711f2ee27d
docker.io/bitnami/kafka:3.3.1-debian-11-r11,sha256:be29db0e37b6ab13df5fc14988a4aa64ee772c7f28b4b57898015cf7435ff662
docker.io/bitnami/mongodb:6.0.3-debian-11-r0,sha256:e7438d7964481c0bcfcc8f31bca2d73022c0b7ba883143091a71ae01be6d9edb
docker.io/bitnami/postgresql:14.1.0-debian-10-r80,sha256:6eb9c4ab3444e395df159e2cad21f283e4bf30802958467590c886f376dc9959
docker.io/bitnami/zookeeper:3.8.0-debian-11-r47,sha256:0f3169499c5ee02386c3cb262b2a0d3728998d9f0a94130a8161e389f61d1462

CodePudding user response：

You are trying to use Perl extensions which are not supported by more traditional regex tools like sed and Awk.

If I can guess what you are trying to do, you want simply

sed -i 's/,[^@]*@/,/g' temp

The /g flag is unnecessary if you only expect one match per line.

Neither , nor @ is a regex metacharacter; they do not require escaping.

Usually you would want to avoid using a temporary file or sed -i; perhaps simply

kubectl blah blah | sed 's/,[^@]*@/,/' > temp

to create the file, or remove the redirection if you want to pipe the results further.