Lab46 Wiki

File Archival

File archival, sometimes referred to as concatenating files, is used to join multiple files and data regarding those files into a single file which can then be compressed to reduce the amount of required storage space needed for files. Each computer platform or operating system has their own formats for concatenating files. Tar, ar, and shar are the file formats used by Unix operating system to join the files and gzip is the format of the compressed file. Each format is distinct in the treatment of the files. For example, the tar format is used for the creation of tape archives, and has replaced the ar format for most files other than static libraries. The shar format is for shell script archives.

List any sites, books, or sources utilized when researching information on this topic. (Remove any filler text).

• http://en.wikipedia.org/wiki/Archive_file
• http://www.computerhope.com/unix/utar.htm
• http://en.wikipedia.org/wiki/Ar_(Unix)

Data Streams (STDIN, STDOUT, STDERR)

Data Streams: Incoming and outgoing information between commands, files, programs and the computer.

Standard Input (STDIN)

  Data being accepted as incoming information into another command, file or program. 
  

Standard Output (STDOUT)

  The information displayed or redirected from a command, file or program.
  

Standard Error (STDERR)

  The message displayed when a problem occurs with a command, file or program. This message can be redirected like standard output
  as long as the file descriptor "2" is used before the redirect indicator.  

1. Unix for the Beginning Mage A Tutorial by Joe Topjian

Demonstration of Data Streams.

In the example below, the STDOUT of the who command is being piped as STDIN to the wc-l command. The STDOUT of the wc -l command is the number 9, which in this example is simply displayed on screen.

lab46:~$ who | wc -l
9

In the first example below, the STDERR message is displayed on screen from a bad command. The second example shows the STDERR message being redirected to a file, and the cat command used to display contents of file.

lab46:~$ ls files
ls: cannot access files: No such file or directory

lab46:~$ ls files 2> error.txt
lab46:~$ cat error.txt
ls: cannot access files: No such file or directory