I have just started pset6 and i am trying to run staff's implementation. However I am getting error as shown in picture below. Kindly suggest the fix. Thanks

~/workspace/ $ cd /home/cs50
/home/cs50/ $ cd pset6
/home/cs50/pset6/ $ ls
/home/cs50/pset6/ $ server
bash: server: command not found
/home/cs50/pset6/ $ server*
bash: server: command not found
/home/cs50/pset6/ $ cd Dropbox
bash: cd: Dropbox: No such file or directory
  • Make sure you are using the correct version of the specification. CS50x 2015 mentions "Dropbox" in the instructions. CS50x 2016 does not. Correct specification can be found here. The assignment changed very much between the two terms. Commented Oct 7, 2016 at 13:55

1 Answer 1


When you execute a program from the command line, you need to provide either an absolute pathname or a relative pathname to the executable file, unless the executable is located in a directory which is specified in your shell's $PATH environment variable.

Absolute pathnames start relative to the root directory:


or this shorter version:


The second one works because ~cs50 is equivalent to /home/cs50.

Using an absolute pathname like this should fix your problem. You will not even need to cd to the CS50 Staff's home directory.

Relative pathnames start relative to the current working directory:

cd /home/cs50/pset6

or like this:

cd /home/cs50

or even like this:

cd /home/ubuntu

When you type server by itself on a line, instead of ./server (assuming that your working directory is /home/cs50/pset6) the shell looks for the server command in all the directories on your $PATH.

In the IDE, the $PATH is long and maybe a bit overwhelming:

~/workspace/ $ echo $PATH

In the Appliance, the $PATH is shorter and easier to read:

jharvard@appliance (~): echo $PATH

Since there is no executable binary or script file named server in any of those locations, the bash shell responds with the helpful error message:

bash: server: command not found

The error message tells you three things. Most obviously, it tells you "command not found" -- something you typed was not found on the $PATH.

Less obviously, it also tells you where the error is coming from ("bash:" -- the "Bourne Again SHell" command interpreter) and also what invalid command you tried to execute.

~/workspace/ $ waleed
bash: waleed: command not found

Hope this helps.

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