OPERATORS
   Listed in order of decreasing precedence:

   ( expr )
          Force precedence.  Since parentheses are special to the shell, you will normally need  to  quote  them.
          Many  of  the  examples  in  this  manual  page  use backslashes for this purpose: `(...)' instead of
          `(...)'.

   ! expr True if expr is false.  This character will also usually need protection  from  interpretation  by  the
          shell.

   -not expr
          Same as ! expr, but not POSIX compliant.

   expr1 expr2
          Two  expressions in a row are taken to be joined with an implied -a; expr2 is not evaluated if expr1 is
          false.

   expr1 -a expr2
          Same as expr1 expr2.

   expr1 -and expr2
          Same as expr1 expr2, but not POSIX compliant.

   expr1 -o expr2
          Or; expr2 is not evaluated if expr1 is true.

   expr1 -or expr2
          Same as expr1 -o expr2, but not POSIX compliant.

   expr1 , expr2
          List; both expr1 and expr2 are always evaluated.  The value of expr1 is discarded;  the  value  of  the
          list is the value of expr2.  The comma operator can be useful for searching for several different types
          of thing, but traversing the filesystem hierarchy only once.  The -fprintf action can be used  to  list
          the various matched items into several different output files.

   Please note that -a when specified implicitly (for example by two tests appearing without an explicit operator
   between them) or explicitly has higher precedence than -o.  This means that find . -name afile -o -name  bfile
   -print will never print afile.

#include <stdio.h>

int main (int argc, char **argv) {
        printf("THIS IS PGM1. I RETURN FALSE.n");
        return 1;
}

#include <stdio.h>

int main (int argc, char **argv) {
        printf("THIS IS PGM2. I RETURN TRUE.n");
        return 0;
}

lalev@dragonfly:~/example10$ ls -l
total 32
-rwxrwxr-x 1 lalev lalev 8296 Jan 18 12:16 pgm1
-rw-rw-r-- 1 lalev lalev  112 Jan 18 12:16 pgm1.c
-rwxrwxr-x 1 lalev lalev 8296 Jan 18 12:16 pgm2
-rw-rw-r-- 1 lalev lalev  111 Jan 18 12:16 pgm2.c
-rw-rw-r-- 1 lalev lalev    0 Jan 17 23:10 test1
lalev@dragonfly:~/example10$ find . -exec ./pgm1 ; -o -exec ./pgm2 ; -print
THIS IS PGM1. I RETURN FALSE.
THIS IS PGM2. I RETURN TRUE.
.
THIS IS PGM1. I RETURN FALSE.
THIS IS PGM2. I RETURN TRUE.
./pgm1.c
THIS IS PGM1. I RETURN FALSE.
THIS IS PGM2. I RETURN TRUE.
./pgm1
THIS IS PGM1. I RETURN FALSE.
THIS IS PGM2. I RETURN TRUE.
./pgm2
THIS IS PGM1. I RETURN FALSE.
THIS IS PGM2. I RETURN TRUE.
./test1
THIS IS PGM1. I RETURN FALSE.
THIS IS PGM2. I RETURN TRUE.
./pgm2.c
lalev@dragonfly:~/example10$