22.21 How to Change File Ownership Without chown

UNIX systems with disk quotas (24.17) won't let you change the owner (22.20) of a file; only the superuser can use chown. Here's a workaround for those systems.

1. The file's current owner should make sure that the new owner has write permission on the directory where the file is and read permission on the file itself:

   jerry% ls -ld . afile
   drwxr-xr-x   2 jerry    512  Aug 10 12:20 .
   -rw-r--r--   1 jerry   1934  Aug 10 09:34 afile
   jerry% chmod go+w .

2. The new owner (logged in as herself) should rename the file, make a copy, and delete the original file. If the new owner is there at the same time, su (22.22) is probably the fastest way to change accounts:

   -f	jerry% su laura Password: laura% mv afile afile.tmp laura% cp -p afile.tmp afile laura% ls -l afile -rw-r--r-- 1 laura 1934 Aug 10 09:34 afile laura% rm -f afile.tmp laura% exit jerry% chmod go-w .

The cp -p (18.15) command preserves the file's original permissions and last modification time. After the new owner (laura) is done copying, the old owner (jerry) takes away the directory's write permission again.