Updated: April 17, 2012
Applies To: Windows Vista, Windows Server 2008, Windows Server 2012, Windows 8
Compares the contents of two files or sets of files byte-by-byte. If used without parameters, comp prompts you to enter the files to compare.
For examples of how to use this command, see Examples.
comp [<Data1>] [<Data2>] [/d] [/a] [/l] [/n=<Number>] [/c]
Specifies the location and name of the first file or set of files that you want to compare. You can use wildcard characters (* and ?) to specify multiple files.
Specifies the location and name of the second file or set of files that you want to compare. You can use wildcard characters (* and ?) to specify multiple files.
Displays differences in decimal format. (The default format is hexadecimal.)
Displays differences as characters.
Displays the number of the line where a difference occurs, instead of displaying the byte offset.
Compares only the number of lines that are specified for each file, even if the files are different sizes.
Performs a comparison that is not case-sensitive.
Processes files with the offline attribute set.
Displays Help at the command prompt.
How the comp command identifies mismatching information
During the comparison, comp displays messages that identify the locations of unequal information between the files. Each message indicates the offset memory address of the unequal bytes and the contents of the bytes (in hexadecimal notation unless the /a or /d command-line parameter is specified). Messages appear in the following format:
Compare error at OFFSET xxxxxxxx
file1 = xx
file2 = xx
After ten unequal comparisons, comp stops comparing the files and displays the following message:
10 Mismatches - ending compare
Handling special cases for Data1 and Data2
If you omit necessary components of either Data1 or Data2 or if you omit Data2, comp prompts you for the missing information.
If Data1 contains only a drive letter or a directory name with no file name, comp compares all of the files in the specified directory to the file specified in Data1.
If Data2 contains only a drive letter or a directory name, the default file name for Data2 is the same as that in Data1.
If comp cannot find the file(s) you specify, it prompts you with a message to determine whether you want to compare more files.
Comparing files in different locations
Comp can compare files on the same drive or on different drives, and in the same directory or in different directories. When comp compares the files, it displays their locations and file names.
Comparing files with the same names
The files that you compare can have the same file name, provided they are in different directories or on different drives. If you do not specify a file name for Data2, the default file name for Data2 is the same as the file name in Data1. You can use wildcard characters (* and ?) to specify file names.
Comparing files of different sizes
You must specify /n to compare files of different sizes. If the file sizes are different and /n is not specified, comp displays the following message:
Files are different sizes
Compare more files (Y/N)?
To compare these files, press N to stop the comp command. Then, rerun the comp command with the /n option to compare only the first portion of each file.
Comparing files sequentially
If you use wildcard characters (* and ?) to specify multiple files, comp finds the first file that matches Data1 and compares it with the corresponding file in Data2, if it exists. The comp command reports the results of the comparison for each file matching Data1. When finished, comp displays the following message:
Compare more files (Y/N)?
To compare more files, press Y. The comp command prompts you for the locations and names of the new files. To stop the comparisons, press N. When you press Y, comp prompts you for command-line options to use. If you do not specify any command-line options, comp uses the ones you specified before.
To compare the contents of the directory C:\Reports with the backup directory \\Sales\Backup\April, type:
comp c:\reports \\sales\backup\april
To compare the first ten lines of the text files in the \Invoice directory and display the result in decimal format, type:
comp \invoice\*.txt \invoice\backup\*.txt /n=10 /d