Shells provide an interactive command line interface for users to launch and manage programs. There are different types of shells like bash, csh, and ksh. The shell prompt and configuration are defined in files like /etc/bashrc. Common shell commands allow users to navigate directories, view and edit files, search for files, manage running processes, and set environment variables. Shells act as an interface between the user and the operating system kernel.

1. Shell & Command

2. Overview of Shells
 What are Shells
 Shell functions
 interactive textual user interface
 operating environment
 facility for launching and managing commands and programs
 programming language
Users
Shell
Kernel

3. Types of Shell

4. Using shells
 View the shell: echo $SHELL
 Change the Shell: /etc/passwd
 Default shell Linux : /bash
 Default shell Unix (SUN/tcsh, AIX/ksh)

5. Using the Command Line
•Command-line interface present a shell.
•The shell prompt is configured by the /etc/bashrc file

6. Using the Command Line

7. Practive 1
• Basic command for Operating:
- pwd, cd
- ls
- touch, mkdir, cp, mv, rm, rmdir
- cat, less, tail, more

8. Practive 2
History Program
 List of the commands of history
 HISTSIZE environment variable in either the
/etc/profile or ~/.profile file.
 Command other: fc

9. Practive 3
Edit text Program
 Vim
 Vi
 Nano

10. Practive 4
 Find - search for files in a directory hierarchy (-name or no, ‘’,” ”,
+n, -n)
find [-H] [-L] [-P] [path...] [expression]
 Locate - find files by name
locate [OPTION]... PATTERN...
The database searched by default: /var/lib/mlocate/mlocate.db
 Grep, egrep, fgrep - print lines matching a pattern
grep [options] PATTERN [FILE...]
 Sed - stream editor for filtering and transforming text
sed [OPTION]... {script-only-if-no-other-script} [input-file]...

11. Practive 5
 Tar - The GNU version of the tar archiving utility (-c, -x, -z, -j)
tar <operation> [options]
 gzip (-d), gunzip (-d), zcat (-d) - gzip, gunzip, zcat - compress
or expand files
 Zip, unzip
 Bzip2 (-z, -d) - a block-sorting file compressor
 Cpio - copy files to and from archives (-i, -o)
Example: find /tmp | cpio -o > etc.cpio
cpio -i < /etc.cpio

12. Managing Processes
 Command or job is executed in a shell.
 Unique process id number or PID.
 Foreground and background
 Create, Monitor, and Kill Processes.
 Ps (tty?, pts?, who, ps), pstree, top, free
ps [options]
 Kill (-9,-15), killall: terminal process
 bg, fg

13. Signal and Kill
 SIGINT 2 Term Interrupt from keyboard
 SIGQUIT 3 Core Quit from keyboard
 SIGILL 4 Core Illegal Instruction
 SIGABRT 6 Core Abort signal from abort(3)
 SIGFPE 8 Core Floating point exception
 SIGKILL 9 Term Kill signal
 SIGSEGV 11 Core Invalid memory reference
 SIGPIPE 13 Term Broken pipe: write to pipe with no readers
 SIGALRM 14 Term Timer signal from alarm(2)
 SIGTERM 15 Term Termination signal

14. Managing Processes

15. Modifying Process Priorities
 Assigned priority level on the system.
 The priority numbers exist on a scale from –20 to 19.
(default priority level is zero)
nice priority command

16. Environment Variables and Settings
 Any command that is executed is a process. Processes
can be initiated by the user,or by the operating system
itself.
 Each process has an associated environment
 Example
 PATH=/bin
 http_proxy=http_proxy://10.10.10.10:8080
 http_proxy=http_proxy://lab:lab@10.10.10.10:8080
 Export, set, unset

17. Editing Environment variables
 The init process and the PATH variable
 init is a parent process for all the other processes of the
system.
 The init path is fixed in the source of the init program
 All the programs that are started from /etc/inittab work in
the init environment