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▲ projektfu 4 hours ago

Here is the part of the test.c source from V7 Unix:

   main(argc, argv)
   char *argv[];
   {
   
    ac = argc; av = argv; ap = 1;
    if(EQ(argv[0],"[")) {
     if(!EQ(argv[--ac],"]"))
      synbad("] missing","");
    }
    argv[ac] = 0;
    if (ac<=1) exit(1);
    exit(exp()?0:1);
   }
So, if the professor was missing the "[" command, they were missing a link. More likely, they had a weird orthodoxy about using "test" instead of "[" because reasons. One good reason to use "test" instead of "[" in a Bourne shell control statement is if you are running a list of commands between "if" and "then", and the test is the last part of the list.

Another good place to use "test" is if you are not in a control statement and you are just setting $?.

Edit: EQ() is defined as:

   #define EQ(a,b) ((tmp=a)==0?0:(strcmp(tmp,b)==0))
   char *tmp;