CODEWITHSUNDEEP
bashawksedgrep
bugnet17
bugnet17

Reputation: 181

bash: Reads a text file and removes specific characters if they exist

I try to get rid of the last slash in the URL, but only if it exists. any ideas? 

tail -1 /var/script/string.txt | grep -oP '(?<=expanded_url":")[^"]+'

response:

https://research.checkpoint.com/ramnits-network-proxy-servers/

The desired output:

https://research.checkpoint.com/ramnits-network-proxy-servers

Upvotes: 1

Views: 59

Answers (2)

RavinderSingh13
RavinderSingh13

Reputation: 133538

If you are ok with awk you could try following too.

var="https://research.checkpoint.com/ramnits-network-proxy-servers/"
echo $var | awk '{sub(/\/$/,"")} 1'

Explanation: Adding explanation for above code now, only for explanation purposes.

var="https://research.checkpoint.com/ramnits-network-proxy-servers/"    ##Creating a variable in shell which has value as OP mentioned.
echo $var | awk '{sub(/\/$/,"")} 1'         ##Sending echo output to awk command here. In awk command using sub to substitute / which comes in end of line with NULL.
                                            ##awk works on method of condition and action, so mentioning 1 is making condition TRUE and not mentioning any action so by default
                                            ##Printing of line/variable value will happen.

EDIT: By seeing your attempt trying to add 1 more solution to avoid many commands combinations here(this will read only last line of Input_file and come out of command then since I have put exit in it).

tac Input_file | awk 'FNR==1 && /xpanded_url\":\"/{sub(/\/$/,"");print;exit}'

EDIT2: Adding single awk command here, in some awk at its END block we can't fetch last line in some we can so adding both kind of solutions whichever works for people.

awk 'END{if($0 ~ /xpanded_url\":\"/){sub(/\/$/,"");print}}'  Input_file
OR
awk '{val=$0}END{if(val ~ /xpanded_url\":\"/){sub(/\/$/,"",val);print val}}'  Input_file

Upvotes: 1

The fourth bird
The fourth bird

Reputation: 163362

You could use a negative lookahead (?:(?!/?").)+ to check what is on the right is not an optional forward slash followed by a double quote. If that is not the case, then take any character and repeat that 1+ times.

See the regex demo

For example:

echo 'expanded_url":"https://research.checkpoint.com/ramnits-network-proxy-servers/"' | grep -oP '(?<=expanded_url":")(?:(?!/?").)+'

Result

https://research.checkpoint.com/ramnits-network-proxy-servers

Upvotes: 1

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