The file
Command
| Command Format: |
| file
filename(s) |
There are many types of files found on
a UNIX system. The file type can be determined by using the file
command. This information can be important when a user is attempting
to open or read a file. Determining the file type can help a user
decide which program or command to use to open the file. The output
from this command will most often be one of the following: Text,
Executable or Data.
- Text - Examples include ASCII
or English text, commands text, and executable shell scripts. This
type of file can be read using the cat or more commands, which are
discussed in this chapter, and can be edited using vi or another
text editor.
- Executable or Binary -
Examples include 32-bit executable and extensible linking format
(ELF) code files and other dynamically linked executables. This
file type indicates that the file is a command or program. The
strings command, which is covered next, will print out readable
characters in this type of file.
- Data - Data files are those
which are created by an application running on the system. In some
cases the type of file is indicated; for example, FrameMaker
document. When the application in which this file was created
cannot be determined by the file command, the output will simply
indicate data file. The only way to read a data file is to
determine which application created it and open the file with
that application.
Note: For information on other
file types, see the man pages.
Figure
shows several examples using the file
command. The first example is a text file. The second is a data file
which must be read by FrameMaker. The third is the cat
command which is an executable. In the first two examples, we change to
the directory where the file is located first. In the third example, we
specify the file using its absolute pathname.
The
strings
command
The
strings
command can be used to print out
readable characters in an executable or binary file. The output
produced by
strings
can be interpreted by someone with a
programming background. The command is introduced here solely as a
method for demonstrating the printable characters of an executable
file. The
strings
command must be used to read an
executable file such as /usr/bin/cat. In Figure ,
the strings
command is followed by the file name
of the command including the absolute pathname. The
strings
command also shows the usage syntax of
the command in most cases.
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Interactive
Media Activity
(Flash,
95 kB) |
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Using
the strings
command
In this media activity, you are logged in as user2 and your current working directory is: /home/user2/dir2. Refer to the Class File Tree Structure by clicking the 'tree' button located on the Menu Bar and type the commands that would accomplish the requested objectives.
Note: Be sure to press enter after each one. Click on step 1 to begin.
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