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Practical Programming in Tcl & Tk, Third Edition by Brent B. Welch

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Opening Files for I/O

The open command sets up an I/O channel to either a file or a pipeline of processes. The return value of open is an identifier for the I/O channel. Store the result of open in a variable and use the variable as you used the stdout, stdin, and stderr identifiers in the examples so far. The basic syntax is:

open what ?access? ?permissions?
					

The what argument is either a file name or a pipeline specification similar to that used by the exec command. The access argument can take two forms, either a short character sequence that is compatible with the fopen library routine, or a list of POSIX access flags. Table 9-6 summarizes the first form, while Table 9-7 summarizes the POSIX flags. If access is not specified, it defaults ...

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