Ndtyjky

I want to remove trailing comma from json as,

{

  "key1": "value1",

  "object": {

    "key2": "value2", // <- remove comma

  },

  "key3": "value3", // <- remove comma

}

I came up with,

tr -d 'n' | 

sed -E 's:,(s*}):1:g' | 

jq .

and it works but I want to get this fully in sed.

I came up with,

sed -E '/,s*$/ { N; s:,s*(ns*},?):1: }'

which works for above input but fails for

{

  "key1": "value1",

  "object": {

    "key2": "value2",

  },

  "key3": "value3",

  "key4": "value4", // <- remove comma

}

as N reads the next line and starts over from the line after next.

// output sed -E '/,s*$/ { N;l }' using l/look command

{

  "key1": "value1",n  "object": {$

  "key1": "value1",

  "object": {

    "key2": "value2",n  },$

    "key2": "value2",

  },

  "key3": "value3",n  "key4": "value4",$

  "key3": "value3",

  "key4": "value4",

}

Update:

Adding another example for testing:

{

  "key1": "value1",

  "object1": {

    "object2": {

      "key2": "value2"

    },

  },

  "key3": "value3",

}

Update:

This is working for whatever I've thrown at it.

sed -E -n 'H; x; s:,(s*ns*}):1:; P; ${x; p}' | 

    sed '1 d'

Explanation:

sed -E -n 'H; x; P; ${x; p}'

-n 'H; x' to get every line appended to the next line in pattern space (except for the last line which is simply printed with ${x; p})

and

s:,(s*ns*}):1:;

to remove the trailing comma in the pattern space.

Since the input seems to be some kind of extension of JSON, you could use a command-line tool intended for such extensions. For example:

$ hjson -j < input.txt

or:

$ any-json --input-format=hjson input.txt

Output in both cases

{

  "key1": "value1",

  "object": {

    "key2": "value2"

  },

  "key3": "value3"

}

Using the hold buffer:

sed '/^ *}/{H;x;s/([^}]),n/1n/;b};x;/^ *}/d' input

This is just a sed exercise, I don't think sed is the right tool for this job. It also needs a newline at the end or that the file ends with a }.

Not an answer with sed but a (python) solution:

# load as python dictionary

d = {

  "key1": "value1",

  "object": {

    "key2": "value2",

  },

  "key3": "value3",

}



import json



json.dumps(d) # valid json string

Here is one in GNU awk. It uses " as field separator and removes commas before [ n]*} from odd fields (outside quotes, will probably fail for "escaped " inside"). Added "key4": "value4,}", to the file:

$ cat file

{

  "key1": "value1",

  "object": {

    "key2": "value2",

  },

  "key3": "value3",

  "key4": "value4,}",

}

The script processes the whole file as a single record (RS="^$") so it might not work for big files as-is:

$ awk '

BEGIN {

    FS=OFS="""

    RS="^$"

}

{

    for(i=1;i<=NF;i++) {                         # or i+=2 and remove the if

        if(i%2)

            $i=gensub(/,([ n]*})/,"\1","g",$i)

    }

}1' file

Output:

{

  "key1": "value1",

  "object": {

    "key2": "value2"

  },

  "key3": "value3",

  "key4": "value4,}"

}