sub command

[Skaperen]

sub.py is my "sub" command. it substitutes one string (arg 2) for another (arg 1) in one or more files or in th stdin/stdout stream for file name "-" (or if no names given).

#!/usr/bin/env python3
from os import rename,remove
from os.path import exists
from subprocess import run
from sys import argv,stderr,stdin,stdout
from time import time as secs
dne = 0
abort = False
if len(argv)<3:
    exit('string substition needs old string in arg 1 and new string in arg2 followed by an optional list of file names.')
exe = argv.pop(0)
old = argv.pop(0)
new = argv.pop(0)
fns = argv if argv else ['-']
for fn in fns:
    if fns.count(fn)>1:
        exit('duplicate file name: '+repr(fn))
    if fn!='-':
        if not exists(fn):
            print('file does not exist: '+repr(fn),file=stderr)
            dne += 1
if dne:
    exit('aborting due to '+str(dne)+' missing file'+'s'[dne==1:])
for fn in fns:
    if fn=='-':
        tn = None
        fi,fo = stdin,stdout
    else:
        tn = fn+'+'+str(int(secs()*3906250))
        fi = open(fn,'r')
        fo = open(tn,'w')
    changed = 0
    for ol in fi:
        nl = ol.replace(old,new)
        if nl!=ol:
            changed += 1
        fo.write(nl)
    fi.close()
    fo.close()
    if changed and fn!='-':
        run(['chmod','--quiet','--reference='+fn,tn])
        run(['chown','--quiet','--reference='+fn,tn])
        rename(fn,fn+'~')
        rename(tn,fn)
    else:
        if tn:
            remove(tn)