sed permission denied when overwriting file

Question

I am trying to use sed to overwrite my index.php file, but I am getting an error:

$ sed -i \'s@@

        

Answer 1

Seems like you have a permission issue on the /tmp dir. (as discussed bellow, you run command in phpshell, so TMP dir can be setted elsewhere than /tmp)

It should looks like :

$ ls -ld /tmp
drwxrwxrwx 333 root root 32768 12 oct.  03:13 /tmp/

explanations

When invoking sed with -i flag, sed create a temporary file in /tmp dir.

---

Proof with strace :

$ strace -f -e trace=file sed -i 's/a/z/' /tmp/a
execve("/bin/sed", ["sed", "-i", "s/a/z/", "/tmp/a"], [/* 94 vars */]) = 0
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
(...)
open("/tmp/sedPSBTPG", O_RDWR|O_CREAT|O_EXCL, 0600) = 4
rename("/tmp/sedPSBTPG", "/tmp/a")      = 0
+++ exited with 0 +++