Section 5.3.2.1.1. How to use vcif

The program may be run under Unix or DOS by typing

vcif filename

where filename is the name of the file to test. If filename is given as the hyphen character -, the program will read standard input. Standard input will also be read if no file name is supplied; this allows the program to be used in a pipeline of commands.

A number of options may be supplied to the program to modify its behaviour. Without these options (i.e. invoked as above) a brief but informative message is written to the standard output channel for each occurrence of what the program perceives to be a syntax error.

For example, for the incorrect sample file of Fig. 5.3.2.1(a), the output is listed in Fig. 5.3.2.1(b).

Figure 5.3.2.1 | top | pdf | (a) An example CIF with a number of syntax errors and (b) the report of the errors produced by vcif.

Note that the sequence number of the line in which the error occurs is printed. The summary error message is output on a single line (longer lines have been wrapped and indented in Fig. 5.3.2.1 for legibility). Where the type of error necessarily affects only a single line, the program can recover and correctly identify errors on subsequent lines. Where possible, unexpected character strings are printed to help the user to identify the error. No attempt is made to assign any meaning to the data names or the data values in the file. Hence the same logical error (the detachment of a standard uncertainty in parentheses from its parent value) is indicated variously as an unexpected text string or as an extraneous loop item, depending on where it occurs in the file. Indeed, in the case of the incorrect number of loop elements, the program makes no attempt to identify which data value or values in the loop might be in error: it simply counts the number of values in a loop and complains when this is not a multiple of the number of data names declared in the loop header.