(c) faisal akkawi & munki lee 2001basic unix commands1 faisal akkawi akkawi@cs.iit.edu...

(c) Faisal Akkawi & Munki Lee 2001 Basic UNIX Commands 1

Basic UNIX Commands

Faisal Akkawi

akkawi@cs.iit.edu

Department of Computer Science

Illinois Institute of Technology

Chicago, IL 60616

(c) Faisal Akkawi & Munki Lee 2001 Basic UNIX Commands 2

Topics Handling Files and Directories Text Editors Compiling and Linking Handling Processes Archiving and Compressing Files Other Useful Commands

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Handling Files and Directories ls : list files cp : copy files mv : move files rm : remove files mkdir : make directories cd : change directories rmdir : remove directories pwd : print working directory chmod : change permission mode umask : set file-creation mode mask

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ls command Syntax

ls [-Options] [name ...] Description

Lists contents of directory. Frequently Used Options

-a List all entries, including . and .. -d Do not list contents of directories -l Long listing -F Mark directories with a '/', etc.

Examples ls -alF

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cp command Syntax

cp [-Options] file1 [file2 ...] target Description

File1 is copied to target. Frequently Used Options

-f Force remove existing file -i Ask before removing existing file -r Copy directory trees

Examples cp p1.c p2.c cp p1.c p2.c mydir

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mv command Syntax

mv [-Options] file1 [file2 ...] target Description

File1 is moved to target. Frequently Used Options

-f Removes existing files without prompting the user -i Asks before removing existing file

Examples mv p*.c mydir

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rm command Syntax

rm [-f] [-i] file . . . rm -r [-f] [-i] dirname . . . [file . . .]

Description Removes files or directories.

Frequently Used Options -f Removal of files without prompting the user -i Interactive removal -r Recursive removal

Examples rm -f p*.o rm -r mydir

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mkdir command Syntax

mkdir [-m mode] [-p] dirname . . . Description

Creates the specified directories. Options

-m Specifies the mode to be used -p Create missing intermediate directories

Examples mkdir -m 700 letter mkdir abc mkdir -p ./abc/def/ghi

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cd command Syntax

cd [directory] Description

Change working directory. If directory is not specified, the value of shell

parameter $HOME is used as the new working directory.

Examples cd cd ./abc/def/ghi cd ..

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rmdir command Syntax

rmdir [-p] [-s] dirname . . . Description

Removes directories. Options

-p Remove the directory dirname and its parent directories which become empty.

-s Suppress the message when –p is in effect Examples

rmdir letter

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pwd command Syntax

pwd Description

Prints the path name of the working (current) directory.

Examples pwd

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chmod command Syntax

chmod [-R] mode file ... chmod [-R] [ugoa]{+|-|=}[rwxXstl] file ...

Description Changes the permissions mode of a file or directory.

Examples chmod 444 file1 chmod ugo+rw p*.c chmod 700 mydir

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umask command – I Syntax

umask [ooo] Description

Sets file-creation mode mask to ooo. The three octal digits refer to read/write/execute permissions for owner, group, and others, respectively.

The value of each specified digit is subtracted from the corresponding ‘digit’ specified by the system for the creation of a file.

If ooo is omitted, the current value of the mask is printed.

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umask command – II Examples

umask 022 removes group and others write permission (files normally created with mode 777 become mode 755; files created with mode 666 become mode 644).

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Text Editors pico

- Simple, easy-to-use text editor vi

- Text editor based on an underlying line editor ex emacs

- Powerful and extensible

- Hard to learn

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pico Layout is very similar to the pine mailer

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vi vi Modes:

Command mode : Normal and initial mode. Other modes return to command mode upon completion. ESC (escape) is used to cancel a partial command.

Input mode : Entered by setting any of the following options: a A i I o O c C s S R . Arbitrary text may then be entered. Input mode is normally terminated with ESC character.

Last line mode : Reading input for : / ? or !.Terminates by typing a carriage return

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Compiling and Linking cc

- C compiler

- Default behavior is ANSI/ISO C make

- Allows programmer to maintain, update, and

regenerate groups of computer programs.

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cc command – I Syntax

cc [-Options] ... file ... Description

*.c are assumed to be C source programs. *.o are compiled object files. a.out is the default output program name.

Frequently Used Options -c Produce an object file -O Invoke optimizer

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cc command – II -o out Name the final output file out. -Dname Define the name to the C macro processor -Idir Seek dir for include files

Examples cc p1.c

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make command Syntax

make [-f makefile] [-eiknpqrsStuwdDPBNMOg] [names]

Frequently Used Options -f makefile Description file is makefile -n Print commands, but do not execute them. -u Build all targets regardless of whether they are

up-to-date or not. Examples

make make –f Project1.mak

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Handling Processes ps : Prints information about active processes kill : Sends a signal to a process ipcs : Reports IPC facilities status ipcrm : Removes IPC resource id

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ps command Syntax

ps [-Options] Description

Prints information about active processes. Frequently Used Options

-A Every process now running -e Same as -A -f Full listing -l Long listing

Examples ps -ef

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kill command Syntax

kill [-signal] pid . . . kill –l (the letter ‘L’ in lowercase)

Description Sends a signal to the specified processes. The value of signal may be numeric or symbolic. Signal 15 is the default signal. kill –l lists the defined signals.

Examples kill 389 kill –3 401 402 kill -HUP 99999

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ipcs command Syntax

ipcs [-Options] Description

Prints information about active IPC facilities. Without options, information is printed for message

queues, shared memory, and semaphores that are currently active in the system.

Frequently Used Options -q Message queues -m Shared memory segments -s Semaphores

Examples ipcs -q

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ipcrm command Syntax

ipcrm [-Options] Description

Removes messages, semaphore or shared memory identifiers.

Frequently Used Options -q msqid Removes the message queue id -m shmid Removes the shared memory segment id -s semid Removes the semaphore id

Examples ipcrm -q 231

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Archiving and Compressing tar : Tape archiver compress, uncompress, zcat : Compresses and

expands data using adaptive Lempel-Ziv coding gzip : Compresses data using Lempel-Ziv coding gunzip, gzcat : Decompresses files created by gzip,

zip, compress, or pack pack, unpack, pcat : Compresses and expands files

using Huffman codes

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tar command - I Syntax

tar key [arguments] [name...] Description

Saves and restores multiple files on a single file. The key argument controls tar's actions.

Frequently Used Functions c Create x Extract from the tape t List files on the tape

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tar command - II Frequently Used Modifiers

v Verbose f Next argument is the name of the

archive

Examples tar cvf my.tar ./mydir1 ./mydir2 tar tvf my.tar tar xvf my.tar

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compress command Syntax

compress [ -f ] [ -v ] [ -c ] [ -V ] [ -d ] [ -b bits ] [ name ... ] Description

Compresses and expands data Compressed file name is *.Z

Frequently Used Options -c Write output on standard output -d Uncompress -v Verbose

Examples compress my.tar compress -d my.tar.Z

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uncompress command Syntax

uncompress [ -f ] [ -v ] [ -c ] [ -V ] [ name ... ] Description

Uncompresses files Same as compress –d

Frequently Used Options -c Write output on standard output -v Verbose

Examples uncompress my.tar.Z

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zcat command Syntax

zcat [ name . . . ] Description

Uncompresses files Same as uncompress –c Writes the uncompressed data on standard output

Examples zcat my.tar.Z > my.tar

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gzip command Syntax

gzip [ -acdfhlLnNrtvV19 ] [-S suffix] [ name . . . ] Description

Compresses and expands data Suffix .gz

Frequently Used Options -c Write output on standard output -d Uncompress -h Help -r Recursive -v Verbose

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gunzip command Syntax

gunzip [ -acfhlLnNrtvV ] [-S suffix] [ name ... ] Description

Uncompresses files (Same as gzip –d ) Automatically detects input format

Frequently Used Options -c Write output on standard output -h Help -r Recursive -v Verbose

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gzcat command Syntax

gzcat [ -fhLV ] [ name . . . ] Description

Uncompresses files (Same as gunzip –c) Writes the uncompressed data on standard output

Examples gzcat myfile.gz > myfile

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pack command Syntax

pack [ - ] [ -f ] name . . . Description

Compresses files Suffix .z Directories cannot be compressed

Options -f Force packing

Examples pack myfile

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unpack command Syntax

unpack name . . . Description

Expands files created by pack Each .z files is replaced by its expanded version The new file has the .z suffix stripped from its name

Examples unpack myfile.z

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pcat command Syntax

pcat name . . . Description

Uncompresses files created by pack Files are unpacked and written to the standard output

Examples pcat myfile.z pcat myfile pcat myfile.z > myfile

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Other Useful Commands grep : search files for a pattern man : on-line reference manuals wc : word, line and byte or character count

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grep command - I Syntax

grep [-E| -F] [-c| -l| -q] [-insvx] pattern_list [file . . .]

Description Searches the input files, selecting lines matching one

or more patterns Frequently Used Options

-i Case-insensitive search -l Write file names only -n Display line number

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grep command - II Examples

grep -i unix p1.c grep -n UNIX *.c *.h ps –ef | grep mary

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man command Syntax

man [-Options] [-M path] [-T macropackage] [ -s section] name ... man [-M path] -k keyword ...

Description On-line reference manuals

Frequently Used Sections 1 User commands and application programs 2 System calls 3 Library functions

Examples man -s 1 mkdir man mkdir man -k pipe

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wc command Syntax

wc [ -c|-m ] [ -lw ] [ file . . . ] Description

Counts lines, words, and characters Options

-c Count the number of bytes -m Count the number of characters -l Count the number of newline characters -w Count the number of words

Examples wc -l *.h *.c