Error at execl: No such file or directory - c

Question

This is an example that our professor gave us for execl(). There are 2 files in a folder, com1.c looks like
#include <stdio.h>
#include <unistd.h>
int main(){
printf("hello...");
fflush(stdout);
execlp("com2","com2",(char*)NULL);
perror("err at execl");
return 1;
}
and com2.c looks like
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
int main(){
write(1, "...you unicorn ;)",13);
return 0;
}
At runtime it gives me this message:
hello...err at execl: No such file or directory
How can I get "hello...... you unicorn ;" ?
Anticipated thanks.

Answer 1

Make sure that the directory containing com2 is in your PATH environment variable.
PATH=$PATH:/path/to/directory
where /path/to/directory is the directory where you put com2.

Answer 2

You haven't specified what OS you're running ... but, in general, the directory that contains the program you wish to exec should be in your $PATH:
https://linux.die.net/man/3/execlp
The execlp(), execvp(), and execvpe() functions duplicate the actions
of the shell in searching for an executable file if the specified
filename does not contain a slash (/) character. The file is sought in
the colon-separated list of directory pathnames specified in the PATH
environment variable.
If this variable isn't defined, the path list
defaults to the current directory followed by the list of directories
returned by confstr(_CS_PATH). (This confstr(3) call typically returns
the value "/bin:/usr/bin".) If the specified filename includes a slash
character, then PATH is ignored, and the file at the specified
pathname is executed.
Note:
On some other systems, the default path (used when the environment
does not contain the variable PATH) has the current working directory
listed after /bin and /usr/bin, as an anti-Trojan-horse measure. Linux
uses here the traditional "current directory first" default path.