The C Shell

The C Shell: "A special form of redirection is used in shell scripts.

calculate << END_OF_FILE
...
...
END_OF_FILE

In this form, the input is taken from the current file (usually the shell script file) until the string following the '<<' is found.

If the special variable, noclobber is set, if any redirection operation will overwrite an existing file, an error message is given and the redirection will fail. In order to force an overwrite of an existing file using redirection, append an exclamation point (!) after the redirection command. For example for the command:

date >! datefile

The file datefile will be overwritten regardless of its existence.

Adding an ampersand (&) to the end of an output redirection command will combine both the standard error and the standard output and place the output into the specified file."

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C shell illustration.