By default, the shell will search for external commands based on the value of the path environment variable. If the command can not be found in any of the directories specified by the path, it searches the current directory. If you specify a path with the command, the shell will not search the path for the specified command. Instead, it only searches the path specified on the command line. C shell expressions have the same precedence as the C language and uses most of the same operators.
All operators work on numbers except the last four.
The last two commands match the string specified to the left operand with the pattern specified to the right of the operator. A command execution is a primitive operand in an expression and is placed between braces. These expressions can be used to test files attributes and compare strings. These commands return a value of one for true and a value of zero if the expression evaluates to false. The table below contains the commands allowed in these expressions.