fc(CMD) 19 June 1992 fc(CMD) Name fc - compare two files and display the differences between them Syntax To make an ASCII comparison, use the following syntax: fc [/a] [/c] [/l] [lbn] [/n] [/t] [/w] [/nnnn] [drive1:][path1]filename1 [drive2:] [path2]filename2 To make a binary comparison, use the following syntax: fc /b [drive1:] [path1]filename1 [drive2:][path2] filename2 Parameters drive1][path1]filename1 Specifies the location and name of the first file you want to com- pare. drive2:][path2]filename2 Specifies the location and name of the second file you want to com- pare. Switches /a Abbreviates the output of an ASCII comparison. Instead of display- ing all the lines that are different, fc displays only the first and last line for each set of differences. /c Ignores the case of letters. /l Compares the files in ASCII mode. fc compares the two files line by line and attempts to resynchronize the files after finding a mismatch. This is the default mode for comparing files that do not have extensions of .EXE, .COM, .SYS, .OBJ, .LIB, or .BIN. /lbn Sets the number of lines for the internal line buffer. The default length of the line buffer is 100 lines. If the files being com- pared have more than this number of consecutive differing lines, fc cancels the comparison. /n Displays the line numbers during an ASCII comparison. /t Does not expand tabs to spaces. The default behavior is to treat tabs as spaces, with stops at each eighth character position. /w Compresses white space (tabs and spaces) during the comparison. If a line contains many consecutive spaces or tabs, the /w switch treats these characters as a single space. When used with the /w switch, fc ignores (and does not compare) white space at the begin- ning and end of a line. /nnnn Specifies the number of consecutive lines that must match before fc considers the files to be resynchronized. If the number of match- ing lines in the files is less than this number, fc displays the matching lines as differences. The default value is 2. /b Compares the files in binary mode. fc compares the two files byte by byte and does not attempt to resynchronize the files after find- ing a mismatch. This is the default mode for comparing files that have extensions of .EXE, .COM, .SYS, .OBJ, .LIB, or .BIN. Notes Reporting differences between files for an ASCII comparison When you use fc for an ASCII comparison, MS-DOS reports differences between two files by displaying the name of the first file, followed by the lines from filename1 that differ between the files, followed by the first line to match in both files. MS-DOS then displays the name of the second file, followed by the lines from filename2 that differ, followed by the first line to match. Using the /b switch for binary comparisons MS-DOS uses the following format to report mismatches found during a binary comparison: xxxxxxxx:yy zz The value of xxxxxxxx specifies the relative hexadecimal address for the pair of bytes, measured from the beginning of the file. Addresses start at 00000000; the hexadecimal values for yy and zz represent the mismatched bytes from filename1 and filename2, respectively. Using wildcards You can use wildcards (? and *) in either of the filenames you specify with the fc command. If you use a wildcard in filename1, fc compares all the specified files to the file specified by filename2. If you use a wildcard in filename2, fc uses the corresponding value from filename1. How fc uses memory When comparing ASCII files, fc uses an internal buffer (large enough to hold 100 lines) as storage. If the files are larger than the buffer, fc compares what it can load into the buffer. If fc does not find a match in the loaded portions of the files, it stops and displays the following message: Resynch failed. Files are too different. When comparing binary files that are larger than available memory, fc compares both files completely, overlaying the portions in memory with the next portions from the disk. The output is the same as that for files that fit completely in memory. Examples Suppose you want to make an ASCII comparison of two text files that are named MONTHLY.RPT and SALES.RPT, and you want to display the results in abbreviated format. To make this comparison, type the following command: fc /a monthly.rpt sales.rpt To make a binary comparison of two batch files named PROFITS.BAT and EARNINGS.BAT, type the following command: fc /b profits.bat earnings.bat The results of this command will be similar to the following: 00000002: 72 43 00000004: 65 3A 0000000E: 56 92 00000012: 6D 5C 00000013: 0D 7C 00000014: 0D 0A 00000015: 0A 0D 0000001E: 43 7A 0000001F: 09 0A 00000022: 72 44 ... ... ... 000005E0: 00 61 000005E1: 00 73 000005E2: 00 73 000005E3: 00 69 000005E4: 00 67 000005E5: 00 6E 000005E6: 00 6D 000005E7: 00 65 000005E8: 00 6E FC: EARNINGS.BAT longer than PROFITS.BAT If the PROFITS.BAT and EARNINGS.BAT files were identical, fc would dis- play the following message: FC: no differences encountered To compare every .BAT file in the current directory with the file NEW.BAT, type the following command: fc *.bat new.bat To compare the file NEW.BAT on drive C with the file NEW.BAT on drive D, type the following command. fc c:new.bat d:*.bat To compare each batch file in the root directory on drive C to the file with the same name in the root directory on drive D, type the following command: fc c:*.bat d:*.bat