Get specific string line from file bash - json

Question

I have a file with this kind of text with pattern
[{"foo":"bar:baz:foo*","bar*":"baz*","etc":"etc"},
{"foo2":"bar2:baz2:foo2*","bar2*":"baz2*","etc":"etc"},
{"foo3":"bar3:baz3:foo3*","bar3*":"baz3*","etc":"etc"},
{"foo4":"bar4:baz4:foo4*","bar4*":"baz4*","etc":"etc"}]
I need to take every string like this
{"foo":"bar:baz:foo*","bar*":"baz*","etc":"etc"} and send each of them to some url via curl
for i in text.txt
do (awk,sed,grep etc)
then curl $string
I can't figure out how to get the desired lines properly from the file without unnecessary symbols

Answer 1

I suggest that you can use jq to process your json file. jq is capable of reading json, and formatting output. Here's an example jq script to process your json file (which I unimaginatively call 'jsonfile'):
jq -r '.[] | "curl -d '\'' \(.) '\'' http://restful.com/api " ' jsonfile
Here's the output:
curl -d ' {"foo":"bar:baz:foo*","bar*":"baz*","etc":"etc"} ' http://restful.com/api
curl -d ' {"foo2":"bar2:baz2:foo2*","bar2*":"baz2*","etc":"etc"} ' http://restful.com/api
curl -d ' {"foo3":"bar3:baz3:foo3*","bar3*":"baz3*","etc":"etc"} ' http://restful.com/api
curl -d ' {"foo4":"bar4:baz4:foo4*","bar4*":"baz4*","etc":"etc"} ' http://restful.com/api
Here's what's going on:
We pass three arguments to the jq program: jq -r <script> <inputfile>.
The -r tells jq to output the results in raw format (that is, please don't escape quotes and stuff).
The script looks like this:
.[] | "some string \(.)"
The first . means take the whole json structure and the [] means iterate through each array element in the structure. The | is a filter that processes each element in the array. The filter is to output a string. We are using \(.) to interpolate the whole element passed into the | filter.
Wow... I've never really explained a jq script before (and it shows). But the crux of it is, we are using jq to find each element in the json array and insert it into a string. Our string is this:
curl -d '<the json dictionary array element>' http://restful.com/api
Ok. And you see the output. It works. But wait a second, we only have output. Let's tell the shell to run each line like this:
jq -r '.[] | "curl -d '\'' \(.) '\'' http://restful.com/api " ' jsonfile | bash
By piping the output to bash, we execute each line that we output. Essentially, we are writing a bash script with jq to curl http://restful.com/api passing the json element as the -d data parameter to POST the json element.
Revisiting for single quote issue
#oguz ismail pointed out that bash will explode if there is a single quote in the json input file. This is true. We can avoid the quote by escaping, but we gain more complexity - making this a non-ideal approach.
Here's the problem input (I just inserted a single quote):
[{"foo":"bar:'baz:foo*","bar*":"baz*","etc":"etc"},
{"foo2":"bar2:baz2:foo2*","bar2*":"baz2*","etc":"etc"},
{"foo3":"bar3:baz3:foo3*","bar3*":"baz3*","etc":"etc"},
{"foo4":"bar4:baz4:foo4*","bar4*":"baz4*","etc":"etc"}]
Notice above that baz is now 'baz. The problem is that a single single quote makes the bash shell complain about unmatched quotes:
$ jq -r '.[] | "curl -d '\'' \(.) '\'' http://restful.com/api " ' jsonfile | bash
bash: line 4: unexpected EOF while looking for matching `"'
bash: line 5: syntax error: unexpected end of file
Here's the solution:
$ jq -r $'.[] | "\(.)" | gsub( "\'" ; "\\\\\'" ) | "echo $\'\(.)\'" ' jsonfile | bash
{"foo":"bar'baz:foo*","bar*":"baz*","etc":"etc"}
{"foo2":"bar2:baz2:foo2*","bar2*":"baz2*","etc":"etc"}
{"foo3":"bar3:baz3:foo3*","bar3*":"baz3*","etc":"etc"}
{"foo4":"bar4:baz4:foo4*","bar4*":"baz4*","etc":"etc"}
Above I am using $'' to quote the jq script. This allows me to escape single quotes using '. I've also changed the curl command to echo so I can test the bash script without bothering the folks at http://restful.com/api.
The 'trick' is to make sure that the bash script we generate also escapes all single quotes with a backslash . So, we have to change ' to \'. That's what gsub is doing.
gsub( "\'" ; "\\\\\'" )
After making that substitution ( ' --> \' ) we pipe the entire string to this:
"echo $\'\(.)\'"
which surrounds the output of gsub with echo $''. Now we are using $' again so the \' is properly understood by bash.
So we wind up with this when we put the curl back in:
jq -r $'.[] | "\(.)" | gsub( "\'" ; "\\\\\'" ) | "curl -d $\'\(.)\' http://restful.com/api " ' jsonfile | bash

Answer 2

Use jq command. This is just example parsing.
for k in $(jq -c '.[]' a.txt); do
echo "hello-" $k
done
Output:
hello- {"foo":"bar:baz:foo*","bar*":"baz*","etc":"etc"}
hello- {"foo2":"bar2:baz2:foo2*","bar2*":"baz2*","etc":"etc"}
hello- {"foo3":"bar3:baz3:foo3*","bar3*":"baz3*","etc":"etc"}
hello- {"foo4":"bar4:baz4:foo4*","bar4*":"baz4*","etc":"etc"}
You can use the $k anywhere inside the loop you want.
for k in $(jq -c '.[]' a.txt); do
curl -d "$k" <url>
done