How can I rename a file on unix using characters in filename?

Question

I have a bunch of files in a unix directory that look like the following:

filename_1234567.txt

I need to rename them by copying the last three characters of each filename to the front of the filename like this:

567_filename_1234567.txt

NOTE: The extension as well as the filename are variable.

I'm running this on a Solaris box.

Answer 1

With zsh:

autoload zmv
zmv -n '*(???).*' '$1_$f'

Remove -n when happy.

Answer 2

So you wish to prepend the last three characters of the file's basename, followed by an underscore, to the front of the filename?

#!/bin/bash
EXT=.txt
for file in *${EXT}; do # presuming all the filenames have no spaces 
   base=${file%${EXT}}
   prefix=${base:(-3)}
   newname=${prefix}_${base}${EXT}
   mv ${file} ${newname}
done

---

This will not work in the Korn shell, as the tricks it uses are bash-specific:

ksh[3]: prefix=${base:(-3)}: bad substitution

---

Answer 3

I like to do something like this:

#!/bin/sh
for i in filename_*.txt; do echo "$i"; done |
sed "s/filename_\([0-9]*\)\([0-9]\{3\}\)\.txt/mv -i 'filename_\1\2.txt' '\2_filename_\1\2.txt'/g"

This prints the list of mv commands to accomplish the task. If it prints the correct commands, then just append | sh at the end of the sed command to cause the shell to execute them.

This script uses the sed subsitute command s and the back reference feature to use parts of the matched regular expression in the replacement string.

s/regex/replacement/

The parts of the regular expression pattern between \( and \) can be referenced in the replacement string by \N where in is a number.

Answer 4

You're on Solaris so you'll have perl. You might even have rename (or possibly prename):

rename -n 's/^(.*)(.{3})(\.[^.]*)$/$2_$1$2$3/' *.*

Remove -n or change it to -v when you're ready to roll.

Answer 5

Pure awk solution: basic idea is to extract last 3 chars of the basename, that means a substring form length - 6 (6 because need to account for the .txt extension) to length - 3. Here I merely extract that substring into VAR first, then create the command complete with mv and two filenames to be ran; finally I ask system function to run the command.

Code:

awk 'BEGIN{
           VAR=sprintf("%s",substr(ARGV[1],length(ARGV[1])-6,3)); 
           CMD=("mv "ARGV[1]" "VAR"_"ARGV[1]); 
           print CMD; 
           system(CMD); 
           close(CMD)
          }' filename_1234567.txt 

Demo:

$ awk 'BEGIN{VAR=sprintf("%s",substr(ARGV[1],length(ARGV[1])-6,3)); CMD=("mv "ARGV[1]" "VAR"_"ARGV[1]); print CMD; system(CMD); close(CMD)}' filename_1234567.txt 
mv filename_1234567.txt 567_filename_1234567.txt
$ ls filename_1234567.txt
ls: cannot access filename_1234567.txt: No such file or directory
$ ls 567_filename_1234567.txt
567_filename_1234567.txt
$