I'll go ahead and post crp.nim here. pjmlp rightly (and often here) observes that people become very trapped in their thinking about PLs. It perhaps helps to emphasize that the whole program generator need not be in the same PL as the generated program. But for the record, I do not think C is a compiled language very well suited to these one-liner tasks. There are probably better ones than Nim, too. My point is mostly about system design. One can probably say that the best backend is probably syntactically non-noisy and easy for whoever your users are. If you are your only user, go nuts some afternoon. :-)

import std/[strutils,os,hashes,sets],cligen/[osUt,mslice] #% exec* mdOpen split
from cligen/parseopt3 import optionNormalize

proc toDef(fields, delim, genF: string): string =
result.add "char const * const rpNmFields = \"" & fields & "\";\n"
let sep = initSep(delim)
let row = fields.toMSlice
var s: seq[MSlice]
var nms: HashSet[string]
sep.split(row, s) # No maxSplit - define every field; Could infer it from the
for j, f in s: #..highest referenced field with a `where` & `stmts` parse.
let nm = optionNormalize(genF % [ $f ]) # Prevent duplicate def errors..
if nm notin nms: #..and warn users about collision.
result.add "int const " & nm & " = " & $j & ";\n"
nms.incl nm
else:
stderr.write "crp: WARNING: ", nm, " collides with earlier field\n"

proc crp(prelude="", begin="", where="1", stmts:seq[string], epilog="",
fields="", genF="$1", comp="", run=true, args="", outp="/tmp/crpXXX",
input="/dev/stdin", delim=" \t", uncheck=false, maxSplit=0): int =
## Gen+Run *prelude*,*fields*,*begin*,*where*,*stmts*,*epilog* row processor
## against *input*. Defined within *where* & every *stmt* are:
## *s[idx]* & *row* => C strings, *i(idx)* => int64, *f(idx)* => double.
## *nf* & *nr* (like *AWK*); NOTE: *idx* is **0-origin**.
## A generated program is left at *outp*.c, easily copied for "utilitizing".
## If you know *AWK* & C, you can learn *crp* PRONTO. Examples (need data):
## **crp 'printf("%s %s\\n", s[1], s[0]);'** # Swap field order
## **crp -w'nr % 100==0' 'printf("%s\\n", row);'** # Prn each 100th row
## **crp -b'int t=0' t+=nf -e'printf("%d\\n", t)'** # Prn total field count
## **crp -b'int t=0' -w'i(0)>0' 't+=i(0)' -e'printf("%d\\n", t)'** # Total>0
## **crp 'float x=f(0)' 'printf("%g\\n", (1+x)/x)'** # cache field 0 parse
## **crp -d, -fa,b,c 'printf("%s %g\\n",s[a],f(b)+i(c))'** # named fields
## Add niceties (eg. `#include "mystuff.h"`) to *prelude* in ~/.config/crp.
let fields = if fields.len == 0: fields else: toDef(fields, delim, genF)
let check = if fields.len == 0: " " elif not uncheck: """
if (nr == 0) {
if (strcmp(row, rpNmFields) == 0) {
nr++; continue; // {fields} {!uncheck}
} else {
exit(2);
}
while ((rpNmRead = getline(&row, &rpNmAlloc, rpNmFile)) != -1) {
row[rpNmRead - 1] = '\0'; // chop newline
${6}s = rpNmSplit(s, &rpNmAlloc, row, "$3", $7, &nf); // {delim,maxSplit}
if ($8) { // {where} auto ()s?
""" % [prelude, fields, delim, indent(begin, 2), input, check, $maxSplit, where]
for i, stmt in stmts:
program.add " " & stmt & "; // {stmt" & $i & "}\n"
if stmts.len == 0:
program.add " /**/;\n"
program.add " }\n nr++;\n }\n"
program.add indent(epilog, 2)
program.add "; // {epilogue}\n}\n"
let mode = if run: "-run" else: ""
let args = if args.len > 0: args else: "-I$HOME/s -O"
let digs = count(outp, 'X')
let hsh = toHex(program.hash and ((1 shl 16*digs) - 1), digs)
let outp = if digs > 0: outp[0 ..< ^digs] & hsh else: outp
let comp = if comp.len > 0: comp else: "tcc $1 $2 -o$3 $4" % [
mode, args, outp, outp & ".c"]
let f = mkdirOpen(outp & ".c", fmWrite)
f.write program
f.close
execShellCmd(comp & (if run: " < " & input else: ""))

when isMainModule:
import cligen; include cligen/mergeCfgEnv
dispatch crp,help={"prelude" : "Nim code for prelude/imports section",
"begin" : "Nim code for begin/pre-loop section",
"where" : "Nim code for row inclusion",
"stmts" : "Nim stmts to run under `where`",
"epilog" : "Nim code for epilog/end loop section",
"fields" : "`delim`-sep field names (match row0)",
"genF" : "make field names from this fmt; eg c$1",
"comp" : "\"\" => tcc {if run: \"-run\"} {args}",
"run" : "Run at once using tcc -run .. < input",
"args" : "\"\" => -I$HOME/s -O",
"outp" : "output executable; .c NOT REMOVED",
"input" : "path to read as input",
"delim" : "inp delim chars for strtok",
"uncheck" : "do not check&skip header row vs fields",
"maxSplit": "max split; 0 => unbounded"}, cmdName="crp"