Files
Overview
The UNIX directory
hierarchy
Filesystems
Manipulating files
Creating
directories
Creating files
links
'Dot' files
Protecting files
Groups
File access
control
Changing
privileges
File
contents
Text files
Comparing
files
Filtering
files
Non-text files
Printing
files
File archives and file
compression
Other relevant commands
Summary
Exercises
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Comparing files
A situation that often arises is that you are examining a file,
and you discover a very similar file, and need to know the
differences between the two files. This can happen when a file has
been edited several times, and you lose track of precisely what
changes have been made. The command diff
('differences') will come to your aid. Use it followed by the names
of two files and it will tell you the changes in the following
manner. Suppose we have two files, file1 and
file2, where file1 contains the following
text:
A
test
file
and file2 contains
A
testing
file
then we would have
$ diff file1 file2
2c2
< test
--
> testing
indicating that line 2 containing myfile has been removed from
file1 and replaced by a line containing
testing. Related to diff is
cmp ('compare'). Sometimes, especially within shell
scripts, the verbosity of diff is not required, and a
terse indication of whether or not two files are identical is
required - cmp will give a short message if its two
arguments are different, otherwise it will stay silent. Also,
diff can only compare text files - cmp
will compare two files of any type and indicate whether or
not their contents are the same.
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