5 ms·

Can't you just use `cat`?

• ben0x539 5y ago
  You cannot use `sudo cat` to open a file with root privileges, because `sudo cat > foo` means "open file foo with your current privileges, then run `sudo cat` passing the file to it", and the whole root thing only happens after you already tried and failed to open the file. I seem to get this wrong roughly once a week.
  • gorgoiler 5y ago
    … | sudo tee foo
  • readme 5y ago
    sudo sh -c "cat > file"
    • deleted 5y ago
      [deleted]
  • icedchai 5y ago
    I knew a person who would give something like this as a sysadmin / devops interview question. It was framed as "'sudo cat >/etc/foo' is giving a permission denied error! what's wrong?" Usually the interview candidate would go off on a tangent...
    • mekster 5y ago
      Will shells or posix standard ever evolve instead of being the obvious gotchas in interviews?
      • icedchai 5y ago
        If Windows can evolve (PowerShell...), so can Linux/Unix.
• HellsMaddy 5y ago
  Cat won’t write the file. If you mean `command | sudo cat > file.txt`, that won’t work because the redirection is still happening in the non-root shell. You could do `command | sudo sh -c "cat > file.txt"` but that’s rather verbose.
• jaden 5y ago
  I thought the same thing. What's wrong with this approach? cat myfile.txt | awk '{do_stuff()}' | sort -u | column --table > new-myfile.txt
  • HellsMaddy 5y ago
    cat is doing nothing useful here. Your command is equivalent to awk '{do_stuff()}' myfile.txt | sort -u | column --table > new-myfile.txt The only thing you’ve changed is that you’re sending the output to a new file. That’s fine, but it’s what sponge is avoiding.