Unix Tutorial

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Unix Tutorial

• CSU480

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Outline

• Getting Started
• System Resources
• Shells
• Special Unix Features
• Text Processing
• Other Useful Commands

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The Unix Operating System

• Kernel
• System calls
• Multi-user, multi-tasking OS

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File System

• FS is the focus point of Unix
• Looks like an inverted tree
• Root directory /
• Each node is either a file or a directory
• Path name
• Absolute path
• Relative path
• . The current directory
• .. The parent of current directory

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Directory, File and I-node

• Every directory and file is listed in its parent
  directory
• The roots parent is itself
• All Unix files are non-structured (bit stream)
• A directory is a special file
• File name
• I-node number

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Unix Programs

• Shell between user and the kernel
• Commands
• Built-in shell command (pwd)
• Source compiled, object code file (ls)
• Shell script (.sh)
• PATH/bin/usr/bin/usr/local/bin, etc

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Getting started

• Logging in
• Linux Command Line Structure
• Control Keys
• stty terminal control
• Getting Help
• Directory Navigation and Control
• File Maintenance Commands
• Display Commands

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Logging in

• Username password
• Unux is case sensitive
• Changing password
• passwd
• Choosing an hard-to-crack password
• Exiting system
• Ctrl-D

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Identity

• usernamelt-gtuserid
• groupnamelt-gtgroupid
• A user can belong to more than one group
• Primary group /etc/passwd
• Additional groups /etc/group

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Identity

• id
• uid1101(frank) gid10(staff)
• id
• uid1101(frank) gid10(staff) groups10(staff),5(
  operator),14(sysadmin),110(uts)
• groups
• staff sysadmin uts operator

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Unix Command Line Structure

• Format command options arguments
• Arguments action object, usu. files
• Options change the way it performs
• command -optionoptionoption
• ls -alR
• command -option1 -option2 -option3
• ls -a -l -R

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Control Keys

• Used to perform special functions
• Ctrl-Key (-Key)
• -U line-kill signal
• -A go to the beginning of the line
• -E go to the end of the line
• -K kill until the end of the line

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Getting Help

• man command
• man -k password
• passwd (5) - password file
• passwd (1) - change password information
• man 5 passwd

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Getting Help
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Directory Navigation and Control
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cd
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mkdir rmdir

• mkdir
• -p create the intermediate (parent) directories,
  as needed
• -m mode access permissions (SVR4).
• rmdir directory must be empty

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ls
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ls
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File Maintenance Commands
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File Maintenance Commands

• cp r recursively copy a directory
• mv Actually all youve done is to update the
  directory table entry to give the file a new
  name. The contents of the file remain where they
  were.
• rm Actually, all youve done is to remove the
  directory table entry and mark the inode as
  unused. The file contents are still on the disk,
  but the system now has no way of identifying
  those data blocks with a file name.
• -r recursively
• -f force

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chmod

• u user
• g group
• o other

read4, write2, execute1 or readr, writew,
executex
add permissions - remove permissions set
permissions
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chmod

• chmod 755 file1 or chmod urwx,gorx file1
• As for directory
• r can read the content of the directory
• w can create/delete files of the directory
• x can go through the directory

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chown

• chown new_usernew_group file
• Note On most versions of Unix this can only be
  done by the super-user, i.e. a normal user cant
  give away ownership of their files.

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Display Commands
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echo
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echo
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more, less, pg
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more, less, pg
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System Resources
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df

• df is used to report the number of disk blocks
  and inodes used and free for each file system.
• Options
• -l local file systems only (SVR4)
• -k report in kilobytes (SVR4)

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du

• du reports the amount of disk space in use for
  the files or directories you specify.
• Options
• -a display disk usage for each file, not just
  subdirectories
• -s display a summary total only
• -k report in kilobytes (SVR4)

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ps

• ps is used to report on processes currently
  running on the system.
• Options
• -e Select all processes.
• -f does full-format listing.

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kill
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who

• who reports who is logged in at the present time.
• Syntax
• who am i

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whereis
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which

• which will report the name of the file that is be
  executed when the command is invoked. This will
  be the full path name or the alias thats found
  first in your path.
• Syntax
• which command(s)

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hostname/uname

• hostname (uname -n on SysV) reports the host name
  of the machine the user is logged into
• uname has additional options to print information
  about system hardware type and software version.

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script

• script creates a script of your session input and
  output. Using the script command, you can capture
  all the data transmission from and to your
  terminal screen until you exit the script
  program. This can be useful during the
  programming-and-debugging process, to document
  the combination of things you have tried, or to
  get a printed copy of it all for later perusal.
• Syntax
• script -a file lt. . .gt exit

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date

• date displays the current data and time. A
  superuser can set the date and time.
• Syntax
• date options format

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Shells

• The shell sits between you and the operating
  system, acting as a command interpreter.
• cat /etc/shells
• /bin/sh
• /bin/bash
• /sbin/nologin
• /bin/ash
• /bin/bsh
• /bin/ksh
• /usr/bin/ksh
• /usr/bin/pdksh
• /bin/tcsh
• /bin/csh
• /bin/zsh

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Shells

• sh Bourne shell (not suited for interactive)
• csh uses C type syntax (job control)
• ksh Korn shell
• bash Bourne Again Shell (GNU)
• tcsh T-C shell
• cshe extended C shell

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Built-in Commands

• These commands are executed directly in the shell
  and dont have to call another program to be run.

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Environment Variables

• Environmental variables are used to provide
  information to the programs you use.
• Global environment variables are set by your
  login shell and new programs and shells inherit
  the environment of their parent shell.
• Local shell variables are used only by that shell
  and are not passed on to other processes.

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Environment Variables
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Shell profile

• Global
• /etc/profile
• User
• /home/duanjj/.bash_profile

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profile

• comments
• PATH separated by a colon and dot .
  represents current directory
• A variable set in .profile is set only in the
  login shell unless you "export" it or source
  .profile from another shell.
• umask 0022

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Job control

• put jobs into the background
• Ctrl-Z suspend a job
• bg put jobs into the background
• fg bring jobs back to the foreground
• jobs list your background jobs

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Job control

• Background jobs cant read from keyboard, but
  they can write onto the terminal, interspersing
  with whatever else is typed or displayed by your
  current job.
• Solution You may want to redirect I/O to or from
  files for the job you intend to background.
• Your keyboard is connected only to the current,
  foreground, job.

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Changing your shell

• chsh
• /etc/shells

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Working With Files
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cmp

• reports the location of the first difference
• can deal with both binary and ASCII file
  comparisons.
• does a byte-by-byte comparison

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diff

• compares two files, directories, etc, and reports
  all differences between the two.
• deals only with ASCII files.
• Its output format is designed to report the
  changes necessary to convert the first file into
  the second.

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cut

• allows a portion of a file to be extracted for
  another use.

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cut

• File users
• cut -f 1,2 users
• cut -c 1-4 users

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paste

• allows two files to be combined side-by-side.
• The default delimiter between the columns in a
  paste is a tab
• A hyphen (-) in place of a file name is used to
  indicate that field should come from standard
  input.

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paste

• users phone
• method 1
• cut f 2 phone gt temp.file
• paste users temp.file gt listing
• method 2
• cut -f2 phone paste users - gt listing

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touch

• used to create a new (empty) file
• or to update the last access date/time on an
  existing file

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wc word count

• Options
• -c count bytes
• -l count lines
• -w count words
• wc users

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ln link to another file

• Syntax
• ln options source target
• Options
• -s make a symbolic link
• hard link
• symbolic link

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Hard link

• Only on the same file system
• Can link to a directory
• creates a new directory entry pointing to the
  same inode as the original file.
• The file linked to must exist before the hard
  link can be created.
• The file will not be deleted until all the hard
  links to it are removed

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Symbolic link

• Used to create a new path to another file or
  directory.
• Can traverse file systems
• Permissions are open to all

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sort - used to order the lines of a file.
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example

• File users
• sort users
• sort 2 users
• sort -r users
• who cut -d " " -f 1 sort -u wc -l

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tee copy command output

• sends standard in to specified files and also to
  standard out.
• often used in command pipelines.
• who tee users.file
• who tee users wc -l

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uniq

• filters duplicate adjacent lines from a file.

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find

• recursively search the indicated directory tree
  to find files matching a type or pattern you
  specify
• then list the files or execute arbitrary commands
  based on the results.
• Syntax
• find directory search options actions
• Common Options
• For the time search options the notation in days,
  n is
• n more than n days
• n exactly n days
• -n less than n days

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find

• find . -newer library -print
• find /usr/include stdio.h -print

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File compression

• gzip, gunzip
• bzip2, bunzip2

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tar archive files

• combines files into one device or filename for
  archiving purposes.
• does not compress the files
• merely makes a large quantity of files more
  manageable.
• accept its options either with or without a
  preceding hyphen (-).

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tar

• Options
• c create an archive (begin writting at the
  start of the file)
• t table of contents list
• x extract from an archive
• v verbose
• f archive file name
• b archive block size

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od

• dumps a file to stdout in different formats,
  including octal, decimal, floating point, hex,
  and character format.
• -b octal dump
• -d-D decimal (-d) or long decimal (-D) dump
• -s-S signed decimal (-s) and signed long
  decimal (-S) dump
• -f-F floating point (-f) or long (double)
  floating point (-F) dump
• -x-X hex (-x) or long hex (-X) dump
• -c-C character (single byte) or long character
  dump (single or multi- byte characters, as
  determined by locale settings) dump
• -v verbose mode

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Thanks