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Description of problem: when I apply "sed -i" on a symbolic link of a file (for instance /etc/grub.conf), sed will remove the symbolic link and create a file. Version-Release number of selected component (if applicable): sed-4.2.1-1.fc11.i586 sed-4.2.1-1.fc11.x86_64 How reproducible: always Steps to Reproduce: root# echo "abc" > x1 root# ln -s x1 x2 root# sed -i 's/abc/cba/' x2 Actual results: root# ls -l x? -rw-r--r--. 1 root root 4 2009-10-30 10:06 x1 -rw-r--r--. 1 root root 4 2009-10-30 10:07 x2 root# cat x? abc cba Expected results: root# ls -l x? -rw-r--r--. 1 root root 4 2009-10-30 10:06 x1 lrwxrwxrwx. 1 root root 2 2009-10-30 10:06 x2 -> x1 root# cat x? abc abc Additional info: none
This is mentioned in i/usr/share/doc/sed-4.2.1/BUGS: -i clobbers read-only files In short, `sed d -i' will let one delete the contents of a read-only file, and in general the `-i' option will let one clobber protected files. This is not a bug, but rather a consequence of how the Unix filesystem works. The permissions on a file say what can happen to the data in that file, while the permissions on a directory say what can happen to the list of files in that directory. `sed -i' will not ever open for writing a file that is already on disk, rather, it will work on a temporary file that is finally renamed to the original name: if you rename or delete files, you're actually modifying the contents of the directory, so the operation depends on the permissions of the directory, not of the file). For this same reason, sed will not let one use `-i' on a writeable file in a read-only directory, and will break hard or symbolic links when `-i' is used on such a file. You can use --follow-symlinks to get the desired behavior.
Ciao Paolo but this is a new feature, isn't it? For instance I have not this problem with RHEL 5.4: root# rpm -qa sed sed-4.1.5-5.fc6 On RHEL 5.4 I have another problem: sed on a symbolic link works only with the full path: root# sed -i 's/abc/cba/' x2 sed: ck_follow_symlink: couldn't lstat x/x1: No such file or directory root# sed -i 's/abc/cba/' /tmp/sed/x2 and this without the "--follow-symlinks" option (which doesn't exist for this version): root# ls -l x? -rw-r--r-- 1 root root 4 Oct 30 12:31 x1 lrwxrwxrwx 1 root root 2 Oct 30 12:31 x2 -> x1 ... Thx, Michele
The RHEL bug is bug 490473. I added you to the CC list there. The Fedora behavior is "a new feature" indeed, or you could say it was a bug before in that it did not follow what the manual said. It's a bit unfortunate either way, I agree.