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An existence check before reading a file can catch and/or prevent a fatal error, for instance. For that reason, most programming language libraries contain a means of checking whether a file exists. An existence check can sometimes involve a " brute force " approach of checking all records for a given identifier, as in this Microsoft Excel ...
See also: the {{}} template. The #if function selects one of two alternatives based on the truth value of a test string. {{#if: test string | value if true | value if false}} As explained above, a string is considered true if it contains at least one non-whitespace character.
For example, C, C++ and their many derivatives support block comments delimited by /* and */ and line comments delimited by //. Other languages support only one type of comment. Other languages support only one type of comment.
This technique can either supplement or complement timestamps and versioning. It can configure an alternative if, for example, a status column is set up on a table row indicating that the row has changed (e.g., a boolean column that, when set to true, indicates that the row has changed).
In MS-DOS, a batch file can be started from the command-line interface by typing its name, followed by any required parameters and pressing the ↵ Enter key. When DOS loads, the file AUTOEXEC.BAT, when present, is automatically executed, so any commands that need to be run to set up the DOS environment may be placed in this file.
Stored procedures may also contain declared variables for processing data and cursors that allow it to loop through multiple rows in a table. Stored-procedure flow-control statements typically include IF, WHILE, LOOP, REPEAT, and CASE statements, and more. Stored procedures can receive variables, return results or modify variables and return ...
Finding an entry in the auxiliary index would tell us which block to search in the main database; after searching the auxiliary index, we would have to search only that one block of the main database—at a cost of one more disk read. In the above example the index would hold 10,000 entries and would take at most 14 comparisons to return a result.
grep is a command-line utility for searching plaintext datasets for lines that match a regular expression.Its name comes from the ed command g/re/p (global regular expression search and print), which has the same effect.