Ubuntu – the difference between “>” and “>>”

If we leave edge cases to one side, the difference is simple. Control+C aborts the application almost immediately while Control+Z shunts it into the background, suspended.

The shell send different signals to the underlying applications on these combinations:

• Control+C (control character intr) sends SIGINT which will interrupt the application. Usually causing it to abort, but this is up to the application to decide.

• Control+Z (control character susp) sends SIGTSTP to a foreground application, effectively putting it in the background, suspended. This is useful if you need to break out of something like an editor to go and grab some data you needed. You can go back into the application by running fg (or %x where x is the job number as shown in jobs).

  We can test this by running nano TEST, then pressing Control+Z and then running ps aux | grep TEST. This will show us the nano process is still running:

  oli     3278  0.0  0.0  14492  3160 pts/4    T    13:59   0:00 nano TEST
  

  Further, we can see (from that T, which is in the status column) that the process has been stopped. So it's still alive, but it's not running... It can be resumed.

  Some applications will crash if they have ongoing external processes (like a web request) that might timeout while they're asleep.

They will behave differently in at least two cases:

• In a chroot, if the link target is outside the chroot, the link will be dead. A bind mount will still be accessible.
• Several programs can distinguish between symbolic links and actual directories or files. Few (if any) can distinguish between a directory or file and the one mounted on it. This also extends to symbolic links to something (A) which have something else (B) mounted on them. The link will show the contents of mount target (B) instead of the original (A).

Also, you can bind mount a directory or file on an existing directory or file, masking the original contents (rendering the original contents inaccessible unless the original was bind mounted elsewhere). A symbolic link requires that the original be moved or deleted.