Need to batch rename files with names from text file using core utils

Question

So I am a bit of a noob and have a problem at work. There is a program outputs names in a ie

apple
banana
orange
P1n34ppl3

The problem is that the files that correspond to that (separate program) are just in 1.txt 2.txt and so on. Is there a way to iterate through the files in a given directory renaming them to the names in the text file using just the core utils ie mv, ls, grep, awk, sed. The system is a standalone RHEL box that is kind of old and no way to get patches or connect to repos with new programs.

Answer 1

Assuming there are as many non-hidden files in the current working directory as there are lines in the output of your-program and that none of the names of the files contain newline characters, you could do in a shell with support for ksh-style process substitution (ksh, zsh, bash):

paste -d '\n' <(ls -v) <(your-program) | xargs -rn2 -d '\n' echo mv --

(and remove the echo if that looks OK).

ls with -v sorts numerically so that for instance 10.txt comes between 9.txt and 11.txt instead of between 1.txt and 2.txt with the normal lexical order.

paste zips the lines of ls and those of your-program.

xargs gets two lines at a time to pass to mv.

-v, -r, -d are GNU extensions, but your system should have GNU utilities.

If you have zsh, you can do it a lot more reliably with:

files=( *(Nn) ) # or *.txt(Nn) or <->.txt(Nn) for number.txt only
lines=( ${(f)"$(your-program)"} )
for old new (${files:^lines}) echo mv -- $old $new