Older Operating Systems
Older Operating Systems Class Notes # 10 Batch Files (Part 2) October 23, 2003 IF Condition When a given condition is true, the statement is executed. When the given condition is false, the statement is not executed. Figure one illustrates the flow chart for the IF condition. IF entry point No Decision Yes Statement (perform some action) IF exit point Figure 1: IF condition flow chart The IF condition tests the following three conditions: • The ERRORLEVEL of a program • Whether a string is equal to another string • Whether a file exists Using IF to test ERRORLEVEL The syntax for testing the ERRORLEVEL is: IF ERRORLEVEL number command This form of the IF condition determines whether the value of ERRORLEVEL is greater than or equal to a number specified in the number parameter. IF NOT ERRORLEVEL number command This form of the IF condition determines whether the value of ERRORLEVEL is not greater than or equal to a number specified in the number parameter. 1 If the specified condition is true, DOS executes the command specified in the command parameter. Otherwise, DOS skips to the next line in the batch file without executing the command in the command parameter. The only DOS commands that leave an ERRORLEVEL (exit) code are: BACKUP, DISKCOMP, DISKCOPY, FORMAT, GRAFTABL, KEYB, REPLACE, RESTORE, and XCOPY. Many other programs generate exit codes, however. For example, table one contains codes that are generated by the DISKCOPY command. Table one: DISKCOPY codes Code Description 0 The operation was successful. 1 A read/write error occurred that did not terminate the disk copy operation.
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