Previous Chapter Review of Unix.

Review of Unix.

4 Review of Unix.

4.1 Major UNIX variants on campus.

AIX 4.x
Digital Unix 3.x/4.x (originally named OSF/1)
SunOS 4.1.4 (part of Solaris 1.2)
SunOS 5.x (part of Solaris 2.x)
Linux 2.x
IRIX 5.x/6.x
HP/UX 9.x/10.x
Ultrix 4.3a/4.4

4.2 Unix Variants

This diagram shows the "family tree" of the Unix operating system.

SunWorld online publishes a yearly comparison of Unix versions.

4.3 Files.

ls -l to see file types (left most character in listing)

Regular (-)
Directory (d)
Hard Links (-)
Soft Links. (l)
Block special (b)
Character special (c)
Socket (s)
Named pipe (p)
inodes
Modes (chmod command)
umask

4.4 Modes (octal)

4000set user id (SUID) on execution
2000set group id (SGID) on execution
1000save text image after execution (sticky bit)
0x00owner's permissions, where x is OR of:04 (read), 02 (write), 01 (execute)
00x0group's permissions
000xother's permissions

4.4.1 Mode Examples

There are three sets of modes (as shown above). Each set is represented by:

Tabell 2: Mode examples 
-------------------------------------
Octal  Binary  chmod       umask       
               permission  permission  
-------------------------------------
0      000     ---         rwx         
1      001     --x         rw-         
2      010     -w-         r-x         
3      011     -wx         r--         
4      100     r--         -wx         
5      101     r-x         -w-         
6      110     rw-         --x         
7      111     rwx         ---         
-------------------------------------

4.4.2 Command Examples

# chmod 700 file1
# chmod 2755 file2
# chmod 4750 file3

4.5 Processes.

Interactive
Batch (e.g., at command, SunOS and System V batch command, DQS, NQS, etc.)
Daemons
fork()/exec()
ps command (BSD example)

# ps -aux | egrep -v "^root|^lp|^daemon"
# alias pu "ps -aux | egrep '^\!:1|^USER'"
# pu yourname

4.6 fork() / exec()

Here is an diagram that shows how fork()/exec() work. This program shows how the calls are used in a C program.

4.7 BSD filesystem layout

Here is an example of the BSD file system layout.

4.8 System V filesystem layout

Here is an example of the System V.4 file system layout.

4.9 Related articles

"Using truss And trace," Dinah McNutt, Unix Review, October 1995, p. 35

4.10 Example Problems and Reading

List all the partitions on your system, and categorize their use. Which ones change daily/weekly/monthly?
A handy article on how to free up disc space was posted to the comp.sys.hp.hpux Usenet newsgroup.

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