Ny alternative to the “sed -i” command in Solaris

for xml there is http://xmlstar.sourceforge.net/

XMLStarlet is a set of command line utilities (tools) which can be used to transform, query, validate, and edit XML documents and files using simple set of shell commands in similar way it is done for plain text files using UNIX grep, sed, awk, diff, patch, join, etc commands.

you can also use xsltproc and similar tools (saxon).

for json: i also think its better to just use python, ruby, perl and transform it.

You almost have it already:

awk -F'\t' 'NF==13 {print}' infile  > newfile

And, if you're on one of those systems where you're charged by the keystroke ( :) ) you can shorten that to

awk -F'\t' 'NF==13' infile  > newfile

To do multiple files in one sweep, and to actually change the files (and not just create new files), identify a filename thats not in use (for example, scharf), and perform a loop, like this:

for f in list
do
    awk -F'\t' 'NF==13 {print}' "$f" > scharf  &&  mv -f -- scharf "$f"
done

The list can be one or more filenames and/or wildcard filename expansion patterns; for example,

for f in blue.data green.data *.dat orange.data red.data /ultra/violet.dat

The mv command overwrites the input file (e.g., blue.data) with the temporary scharf file (which has only the lines from the input file with 13 fields).  (Be sure this is what you want to do, and be careful.  To be safe, you should probably back up your data first.)  The -f tells mv to overwrite the input file, even though it already exists.  The -- protects you against weirdness if any of your files has a name beginning with -.