Bash substring removal

Question

I have strings in the following pattern: <SOMETHING_1>{<JSON>}<SOMETHING_2>

I want to keep the <JSON> and remove the <SOMETHING_X>blocks. I'm trying to do it with substring removal, but instead of getting

{x:1,action:PLAYING,name:John,description:Some description rSxv9HiATMuQ4wgoV2CGxw}

I keep getting

{x:1,action:PLAYING,name:John,description:Some}

because the whitespace in the description field cuts off the substring.

Any ideas on what to change?

CODE:

string="000{x:1,action:PLAYING,name:John,description:Some description rSxv9HiATMuQ4wgoV2CGxw}401"
string=$1
string=$(echo "${string#*{}")
string=$(echo "${string%}*}")
string={$string}
echo $string

I'm not getting the output you showed. How do you pass the argument to the script? — choroba
– choroba, Commented Jun 2, 2017 at 22:42
Regardless of correctness, the performance overhead of subshells for the command substitutions is a bit unfortunate. — Charles Duffy
– Charles Duffy, Commented Jun 2, 2017 at 22:43
BTW, I suspect rather strongly that the value is actually getting cut off somewhere else -- for instance, if you're passing it into $1 by invoking yourscript $somevar that would cause the problem, on account of needing to be yourscript "$somevar"; everything after the space is going into $2 or a subsequent argument. — Charles Duffy
– Charles Duffy, Commented Jun 3, 2017 at 3:15

Charles Duffy · Accepted Answer · 2017-06-05 20:29:50Z

1

The original code works perfectly, if we accept a direct assignment of the string -- though the following is a bit more explicit:

string="000{x:1,action:PLAYING,name:John,description:Some description rSxv9HiATMuQ4wgoV2CGxw}401"
string='{'"${string#*"{"}"  # trim content up to and including the first {, and replace it
string="${string%'}'*}"'}'  # trim the last } and all after, and replace it again
printf '%s\n' "$string"

...properly emits:

{x:1,action:PLAYING,name:John,description:Some description rSxv9HiATMuQ4wgoV2CGxw}

I'm guessing that the string is being passed on a command line unquoted, and is thus being split into multiple arguments. If you quote your command-line arguments to prevent string-splitting by the calling shell (./yourscript "$string" instead of ./yourscript $string), this issue will be avoided.

edited Jun 5, 2017 at 20:29

answered Jun 2, 2017 at 22:40

Charles Duffy

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1 Comment

Nishant Roy Over a year ago

You were right in your comments above. It was the $1 that was causing it to get cut off. Thanks a ton! Please add that to your answer so I can accept it.

tso · Accepted Answer · 2017-06-03 06:31:36Z

0

with sed:

string="000{x:1,action:PLAYING,name:John,description:Some description rSxv9HiATMuQ4wgoV2CGxw}401"
sed 's/.*\({.*}\).*/\1/g' <<<$string

output:

{x:1,action:PLAYING,name:John,description:Some description rSxv9HiATMuQ4wgoV2CGxw}

answered Jun 3, 2017 at 6:31

tso

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Comments

Shammel Lee · Accepted Answer · 2017-06-04 09:36:21Z

0

Here you go…

string="000{x:1,action:PLAYING,name:John,description:Some description rSxv9HiATMuQ4wgoV2CGxw}401"
echo "original: ${string}"
string="${string#*\{}"
string="${string%\}*}"
echo "final: {${string}}"

By the way, JSON keys should be surrounded with double quotes.

answered Jun 4, 2017 at 9:36

Shammel Lee

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