at-at, batch--execute commands at a later time

Example Explanationat 6:30am Dec 12 < program

At 6:30am in the morning December 12th, start the job

at noon tomorrow < program

At noon tomorrow start the job

at 1945 pm August 9 < program

At 7:45 in the evening on August 9th, start the job

at now + 3 hours < program In three hours start the job

at 8:30am Jan 4 < program At 8:30 in the morning of January 4th, start the job.

at –r 83883555320.a Removes previously scheduled job 83883555320.a

awk--pattern scanning and processing language

Example Explanationawk ‘{print $1, $2}’ file Prints the first two fields of

file where fields are separated by white space

awk ‘/John/ {print $3, $4}’ file

Prints fields 3 and 4 if the pattern John is found

awk –F: ‘{print $3}’ /etc/passwd

Using a colon as the field separator, prints the third field of the /etc/passwd file

date | awk ‘{print $6}’ Sends the output of the date command to awk and prints the sixth field

banner--make posters

Example Explanation

banner Happy Birthday Displays Happy Birthday

basename--with a directory name delivers portions of the pathname

Example Explanation

basename /usr/location Strips off the prefix /usr/local and displays bin

scriptname=“’basename $0’”

Assigns just the name of the scriptname, $0, to the variable scriptname

bc--processes precision arithmetic

Example Explanation

bc << EOFscale=34.5+5.63EOF Output : 6.366

This is a here document. From the first EOF to the last EOF input is given to the bc command. The scale specifies the number of digits to the right of the decimal point. The result of the calculation is displayed on the screen

bc ibase=25101 (Output)2010100 (Output)^D

The number base is two. The number converted to binary (ATT only)

bdiff—compares two big files

bdiff compares two files that are too large for diff.

cal—displays a calendar

Example Explanation

cal 1997 Prints the calendar year 1997

cal 5 Prints the month of May for 1978

cat—concatenates and displays files

Example Explanationcat /etc/passwd Displays the contents of

the /etc/passwd file

cat –n file1 file2 >> file3

Concatenates file1 and file2 and appends output to file3. The –n switch causes each line to be numbered

chmod—change the permissions mode of a file

Example Explanationchmod +x script.file Turns on execute permission

for user, group, and others on script.file

chmod u+x,g-x file Turns on execute permission for user, and removes it from group on file

chmod 755 * Turns on read, write, and execute for the user, read and execute for the group, and read and execute for others on all files in the current working directory. The value is octal (111 101 101).

chown—changes owner of a file

Example Explanationchown john filex Changes the user id of

filex to john

chown –R ellie ellie Recursively changes the ownership of ellie for all files in ellie directory

clear, clears the terminal screen

cmp—compares two files

Example Explanationcmp file.new file.old If the files differ, the

character number and the line number are displayed

compress—compress, uncompress, zcat compress, uncompress files, or display expanded files

Example Explanation

compress –v bookbook:Compression:35.07% -- replaced with book.Z

Compresses the book into a file book.Z and displays the percentage that the file was compressed and its new name

lsBook.Z

cp — copies files

Example Explanationcp file1 file2 Copies the contents of file1

to file2cp chapter1 book Copies the contents of

chapter1 to the book directory. In the book directory chapter1 has its original name

cp –r desktop /home/tom/docs

Recursively copies the entire desktop directory into /home/tom/docs

cpio —copy file archives in and out

Example Explanationfind . –depth –print | cpio –pmdv homejohn/tmp

Starting at the current directory, find descends the directory hierarchy, printing each of the entries of the directory even if the directory does not have write permission and sends the filenames to cpio to be copied into the john/tmp directory in the /home partition

cron—the clock daemon

cron executes commands at specified dates and times. Regularly scheduled jobs can be specified in the /etc/crontab file. (Must have superuser privileges)

crypt—encode or decode a file

crypt encrypts and decrypts the contents of a file. The password is a key that selects a type of transformation

cut—removes selected fields or characters from each line of a file

Example Explanationcut –d: -f1,3 /etc/passwd Using the colon as field

delimiter, displays fields 1 and 3 of the /etc/passwd file

cut –d: -f15 /etc/passwd Using the colon as a field separator, displays fields 1 through 5 of the /etc/passwd file

cut –c1-3,8-12 /etc/passwd Cuts and displays characters 1 through 3 and 8 through 12 of each line from the /etc/passwd file

date | cut –c1-3 Sends the output of the date commands as input to cut. The first three characters are printed

date—displays the date and time or sets the date

Example Explanation

date +%T Displays the time as 20:25:51

date +20%y Displays 2096

date “+It is now %m/%d /%y”

Displays It is now 07/25/96

diff—compares two files for differences diff [-biw][-c] | -Cn

Example Explanationdiff file1 file21c1< hello there---> Hello there> 2a3 > I’m fine

Shows how each line of file1 and file2 differ. The first file is represented by the < symbol, and the second file by the > symbol. Each line is preceded by an ed command indicating the editing command that would be used to make the files the same

du—summarizes disk usage

Example Explanationdu –s /desktop Displays a summary of

the block usage for all the file in /desktop and its subdirectories

du –a Displays block usage for each file in this directory and subdirectories

echo—echoes arguments

System V echo options\b Backspace

\c Suppress new line

\f Form feed

\n New line

\r Carriage return

\t Tab

\v Vertical tab

\\ Backslash

\0n N is a 1,2, or 3 octal value

egrep—searches a file for a pattern using full regular expressions

Example Explanationegrep ‘Tom|John’ datafile

Displays all lines in datafile containing the pattern either Tom or John

egrep ‘^ [A-Z]+’ Displays all lines starting with one or more uppercase letters

expr—evaluates arguments as an expression

Example Explanationexpr 5 + 4 Prints the sum of 5 +4

expr 5 \* 3 Prints of result 5*3. The asterisk is protected from shell expansion

num=0num=‘expr $num + 1’

After assigning 0 to variable num, the expr command adds 1 to num and results is assigned to num

fgrep—search a file for a character string

Example Explanation

fgrep ‘***’ Displays any line containing three asterisks from each file in the present directory. All characters are treated as themselves; i.e., metacharacters are not special

fgrep ‘ [ ] * ? $’ filex Displays lines in filex containing the string enclosed in quotes

file—determines the type of a file by looking at its contents

Example Explanation

file bin/ls/bin/ls:sparc pure dynamically linked executable

ls is binary file dynamically linked when executed

file gogo: executable shell script

go is a shell script

file junkjunk: English text

junk is a file containing ASCII text

find—finds files

Example Explanationfind . –name \*.c –print Starting at the present

working directory (do), finds all the ending files in dot c and prints the full pathname

find .. –type f –print Starting at the parent directory (dot dot), finds all files of type file; i.e. files that are not directories

finger—displays information about local and remote users

By default, the finger command displays information about each logged in user, including login name, full name, terminal line (prepended with a ‘*’ if write permission is denied), idle time, login time, and location if known

fmt—simple text formatters

Example Explanation

fmt –c –w45 letter Formats letter. The –c switch preserves the indentation of the first two lines within the paragraph and aligns the left margin of each subsequent line with that of the second line. The –w switch fills the output line of up to 45 columns

fold—folds long lines

Fold the contents of the specified filenames, or the standard input if no files are specified, breaking the lines to have maximum width. The default for width is 80. Width should be a multiple of 8 if tabs are present, or the tabs should be expanded

ftp—file transfer program

Example Explanationftp dbase.bridgeport.edu ftp to the machine

dbase.bridgeport.edu , a large repository run by UUNET service which handles e-mail and net news for UNIX systems

ftp –n 216.87.102.26 Opens a connection to the machine at 216.87.102.26 and does not attempt to autologin

getop(s)—parses command line options

The getopts command supersede getop. getops is used to break up options in command lines for easy parsing by shell procedures and to check for legal options.

grep—searches a file or a program

Example Explanationgrep Tom file1 file2 file3 grep displays all lines in file1,

files2, and file3 that contain the pattern

grep –in ‘^ton savage’ * grep displays all lines with line numbers from the files in the current working directory that contain tom savage if tom savage is at the beginning of the line, ignoring case

groups—prints group membership of user

• The command groups prints on standard output the groups to which you or the optionally specified user belong.

id—prints the username, user ID, group name and group ID

• id displays your user ID,user name, group ID, and group name. If your real ID and your effective ID’s do not match, both are printed.

jsh—the standard, job control shell

• The command jsh in an interface to the standard Bourne shell which provides all of the functionality of the Bourne shell and enables job control.

line—reads one line

line copies one line (up to a new line) from the standard input and writes it on the standard output. It returns an exit code of one on EOF and always prints at least a new line. It is often used within shell files to read from the user’s terminal.

logname—gets the name of the user running the process

lp(ATT)—sends output to a printer

Example Explanationlp –n5 filea fileb Send five copies of filea

and fileb to the printer

lp –dShakespeare filex Specify Shakepsepeare as the printer where filex will be printed

lpr(UCB)—sends output to a printer

Example Explanationlpr -#5 filea fileb Send five copies of filea

and filesb to the printer

lpr –PShakespeare filex Specify Shakespeare as the printer where filex will be printed

lpsat(ATT)—print information about the status of the LP print service

lpq(UCB)—print information about the status of the printer

ls —lists a contents of directory

Example Explanationls –alF The –a lists invisible files

(those files beginning with a dot), the –l is a long listing showing attributes of the file, the –F puts a slash at the end of directory filenames, a* at the end of executable script names, and an @ symbol at the end of symbolically linked list

ls-d a* If the argument to the –d switch is a directory, only the name of the directory displayed, not its contents

mail—mail, rmail—read mail or send mail to users

A recipient is usually a username recognized by login. When recipients are named, mail assumes a message is being sent. It reads from the standard input up to an end-of-file(Ctrl-D), or if reading from a terminal, until it reads a line consisting of just a period. When either of those indicators is received, mail adds the letter to the mailfile for each recipient.

mailx—interactive message processing system

The mail utilities listed above provide an interactive interface for sending, receiving, and manipulating mail messages. Basic networking utilities must be installed for some of the features to work. Incoming mail is stored in a file called mailbox, and after it is read, it sends to a file called mbox

make—maintains, updates, and regenerates groups of related program and files

make updates file according to commands listed in a description file, and if the target file is newer than the dependency file of the same name, make will update the target file.

mesg—permits or denies messages resulting from the write command

mesg without argument –n forbids messages via write by revoking no user write permission on the user’s terminal. mesg with argument –y reinstates permission. All by itself, mesg reports the current state without changing it.

mkdir—creates a directory

more—browse or page through a text file

more is a filter that displays the contents of a text file on the terminal, one screenful at a time. It normally pauses after each screenful, and prints “—More—” at the bottom of the screen.

mv—move or rename files

Example Explanation

mv file1 newname Renames files1 to newname. If newname exists its contents are overwritten

mv –i test1 tes2 train Moves files test1 and test2 to the train directory. The –i switch is for interactive mode, meaning is asks first before moving the files

nawk—pattern scanning and processing language

nawk scans each input filename for lines that match any of a set of patterns. The command string must be enclosed in single quotes(‘) to protect it from the shell. awk programs consists of a set of pattern/action statements used to filter specific information from a file, pipe, or stdin.

newgrp—log in to a new group

newgrp logs a user into a new group by changing a user’s real and effective group ID. The user remains logged in and the current directory in unchanged. The execution of newgrp always replaces the current shell with a new shell, even if the command terminates with an error (unknown group)

news—prints mew items

news is used to keep the user informed of current events. By convention, these events are described by files in the directory /var/news. When invoked without arguments, news prints the contents of all current files in /var/news, most recent first, with each preceded by an appropriate header

nice—runs a command at low priority

/usr/bin/nice executes a command with a lower CPU scheduling. The invoking process (generally the user’s shell) must be the time-sharing scheduling class. The command is executed in the time-sharing class. An increment of 10 is the default. The increment must be a range between 1 and 19, unless you are the superuser. Also a csh built-in.

nohup—makes commands immune to hang-ups and quits

Example Explanation

nohup lookup & The lookup program will run in the background and continue to run until it has completed, even if the user logs off. Any output generated goes to a file in the current directory called nohup.out.

od—octal dump

od displays filename in one or more formats, as selected by the first argument. If the first argument is missing, -o is default; e.g., the file can be displayed in bytes octal, ASCII, decimal, hex, etc.

pack—pack, cat, unpack--compresses and expands files

pack compresses files. Wherever possible (and useful), each input file name is replaced by a packed file name.z with the same access modes, access and modified dates, and owner as those of name. Typically, text files are reduced to 60-70% of their original size. pcat does for packed file what cat does for ordinary files, except that pcat cannot be used as a filter. The specified files are unpacked and written to the standard output. Thus to view a packed file named name.z use: pcat name.z or just pcat name. unpack expands files created by pack.

passwd—changes the login password and password attributes

The passwd command changes the password or lists password attributes associated with the user’s login name. Additionally, privileged users may use passwd to install or change passwords and attributes associated with any login name.

paste—merges same line of several files or subsequent lines of one file

Example Explanation

ls | paste - - - Files are listed in three columns and glued together with a TAB

paste –s –s”\t\n” testfile1 testfile2

Combines a pair of lines into a single line using a TAB and new line as the delimiter. The –s switch causes subsequent lines from testfile1 to be pasted first and then subsequent testfile2

pcat—(see “pack”)

pg—displays files a page at a time

The pg command is a filter that allows you to page through one sreenful at a time on a terminal. If no filename is specified or it encounters the file name -, pg reads from standard input. Each screenful is followed by a prompt. If the user types a RETURN, another page is displayed. It allows you to back up and review something that has already passed.

pr—prints file

Example Explanation

pr –2th “TITLE” file1 file2

Prints two columns double sided with header “TITLE” for file1 and file2

ps—reports process status

Example Explanationps –aux | grep ‘^linda” ucb

Prints all processes running and pipes the output to the grep program printing only those processes owned by user linda, where linda is at the beginning of each line

ps –ef |grep ‘^ *linda’ att

Same as the first example, only the ATT version

pwd—displays the present working directory

rcp—remote file copy

Example Explanation

rcp dophin:filename /tmp/newfilename

rcp filename broncos:newfilename

rsh—starts a remote shell

Example Explanation

rsh bluebird ps –ef Connect to machine bluebird and display all processes running on that machine

rsh –l john owl ls; echo PATH. cat .profile

Go to the remote machine owl as user john and execute all three command

ruptime—shows the host status of local machines

ruptime gives a status line like uptime for each machine on the local network; these are formed from packets broadcast by each host on the network once a minute. Machines for which no status has been received for five minutes are shown as being down. Normally, the listing is sorted by host name, but this order can be changed by specifying one of ruptime’s options

rwho—who is logged in on local machine

The rwho command produces output similar to who, but for all machines on your network. However, it does not work through gateways and host must have the directory /var/spool/rwho as well as the rwho daemon running. If no report has been received from a machine for five minutes, rwho assumes the machine is down, and does not report users last known to be logged into that machines. If a user has no typed to the system for a minute or more, rwho reports this idle time. If a user has not typed to the system for an hour or more, the user is omitted from the output of rwho, unless the –a flag is given

script—creates a typescript of a terminal session

Example Explanationscript Starts up a script

session in a new shell. Everything displayed on the terminal is stored in a file called typescript. Must press ^d or exit to end the session

script myfile Starts up a script session in a new shell, storing everything displayed on the terminal in myfile. Must press ^d or exit to end the session

sed—stream editor

Example Explanationsed ‘s/Elizabeth/Lizzy/g’ file

Substitute all occurrences of Elizabeth with Lizzy in file and display on the terminal screen

sed ‘/Dork/d’ file Remove all lines containing Dork and print the remaining lines on the screen

sed –n ‘s5, 20p’ file Print only lines 15 through 20

size—prints section sizes in bytes of object files

The size command produces segment or section size information in bytes for each loaded section in ELF or COFF objects files. size prints out the size of the next, data, and bss (uninitialized data) segments (or section) and their total

sleep—suspends execution for some number of seconds

Example Explanation(sleep 105; command)& After 105 seconds,

command is executed. Prompt returns immediately

(In Script) while true do command sleep 60 done

Enters loop; executes command and sleeps for a minute before entering the loop again

sort—sort and/or merge file

Example Explanationsort filename Sorts the lines alphabetically

sort –u filename Sorts out duplicate entries

sort –r filename Sorts in reverse

sort +1 –2 filename Sorts starting on field 1 stopping at field 2 rather than sorting to the end of line

sort –2n filename Sorts the third field numerically

sort –t: +2n –3 filename Sorts numerically starting at field 3 and stopping at field 4, with the colon designated as the field separator (-t:)

spell—finds spelling errors

spell collects word from the named filenames and looks them up in a spelling list. Words that neither occur among nor are derivable from words in the spelling list are printed on the standard output. If no filenames are named, words are collected from the standard input

split—splits a file into pieces

Example Explanation

split –500 filea Splits filea into 500 line files. Files are named xaa, xab, aac, etc.

split –100 fileb out Splits fileb into 1000 line files names outaa, outab, etc.

strings—finds any printable string in an object or binary file

Example Explanation

strings /bin/awk |head –2

Prints any ASCII text in the first two lines of the binary executable /bin/nawk.

stty—sets the options for a terminal

Example Explanation

stty erase <Press backspace key> or ^h

Sets the backspace key to erase

stty –echo; read secretword; stty echo

Turns off echoing; waits for user input, turns echoing back on

stty –a (ATT) or stty –everything (BSD)

Lists all possible options to stty

su—become super-user or another user

su allows one to become another user without logging off. The default username is root (superuser). To use su, the appropriate password must be supplied (unless the invoker is already root). If the password is correct, su creates a new shell process that has the real and effective user ID, group Ids, and supplementary group list set to those of the specified username. The new shell is specified, sh (Bourne shell) is used. To return to normal user ID privileges, type Ctrl-D to exit the new shell. The - option specifies a complete login.

sum—calculates a checksum for a file

sync—updates the super block and sends changes blocks to disk

tabs—sets tab stops on a terminal

tail—displays the tail end of a file

Example Explanation

tail +50 filex Displays contents of filex starting at line 20

tail –20 filex Displays the last 20 lines of filex

tail filex Displays the last 10 lines of filex

talk—allows you to talk to another user

Example Explanation

talk sbenayed@dbase.bridgeport.edu

Opens a request to talk to user sbenayed on machine called dbase.bridgeport.edu

tar—stores and retrieves files from an archive file, normally a tape device

Example Explanationtar cvf /dev/diskette Sends all files under the

present working directory to tape at device /dev/diskette and prints the files that are being sent

tar tvf /dev/fd0 Displays the table of contents of what is on tape device /dev/fd0

tar xvf /dev/fd0 Extracts from tape all files and prints what files were extracted

tee—replicates file standard output

Example Explanation

date | tee nowfile The output of the date command is displayed on the screen and also stored in nowfile

telnet—communicates with a remote host

Example Explanation

telnet jordan.bridgeport.edu

Opens a session with the remote host jordan.bridgeport.edu

test—evaluates an expression

Example Explanationtest 5 gt 6 The test command

command performs an integer test to see if 5 is greater than 6

echo $? (Bourne and Korn shells)(output is 1, meaning the result of the test is not true.)

The $? Variable contains the exit status of the last command. If a nonzero status is reported, the test results are not true; if the return status is zero, the test result is true

time—displays a summary of time used by this shell and its children

touch—updates access time and/or modification time of a file

Example Explanation

touch a b c Three files, a, b, and c are created. If any of them already exist, the modification timestamp on the files is updated

tput—initializes a terminal or queries the term info database

Example Explanation

tput longname Displays a long name for the terminal from the terminfo database

bold=‘tput smso’Unbold=‘tput rmso’Echo “${bold}Enter your id: ${offbold}\c”

Sets the shell variable bold to turn on the highlighting of displayed text. Then sets the shell variable, unbold, to return to normal text display. The line Enter your id is highlighted in black with white letters. Further text is displayed normally

tr—translates characters

Example Explanationtr ‘A’ ‘B’ < filex Translates As to Bs in

filex

tr ‘[A-Z]’ [a-z] < filex Translates all uppercase letters to lower case letters

tr –d ‘ ‘ < filex Deletes all spaces from filex

tr –s ‘\11’ ‘\11’ , filex Replaces (squeezes) multiple tabs with single tabs in filex

true—provide successful exit status

true does nothing, successfully, meaning that it always returns a zero exit status, indicating success. Used in Bourne and Korn shell programs as a command to start an infinite loopwhile truedo

commanddone

tsort—topological sort

The tsort command produces, on the standard output, a totally ordered list of items consistent with a partial ordering of items mentioned in the input filename. If no filename is specified, the standard input is understood. The input consists of pairs of items (nonempty strings) separated by blanks. Pairs of different items indicate ordering. Pairs of identical items indicate presence, but not ordering

tty—gets the name of the terminal

tty prints the path name of user’s terminal

umask—sets file-creation mode mask for permissions

Example Explanationumask Displays the current file

permission mask

umask 027 The directory permissions, 777, minus the umask is 750. The file permissions, 666, minus the umask 027 is 640. When created, directories and files will be assigned the permissions created by umask

uname—prints name of current machine

Example Explanation

uname –n Prints the name of the host machine

uname –a Prints the operating system name, and the operating system version—same as -m, -r, -s, and –v

uncompress—restores files to their original state after they have been compressed using the compress command

Example Explanation

uncompress file.Z Restores file.Z to its original state; i.e., what was before compressed

uniq—reports on duplicate lines in a file

Example Explanation

uniq file1 file2 Removes duplicate adjacent lines from file1 and puts output file2

uniq –d –2 file3 Displays the duplicate lines where the duplicate starts at third field

units—converts quantities expressed in standard scales to other scales

units converts quantities expressed in various standard scales to their equivalents in other scales. It works interactively in this fashion :You have:inch

You want:cm

*2.540000e+00

/3.937008e-01

unpack—expands files created by pack

unpack expands files created by pack. For each filename specified in the command, a search is made for a file called name.z (or just name, if name ends in .z). If this file appears to be packed file, it is replaced by its expanded version. The new file has the .z suffix stripped from its name, and has the same access modes, access and modification dates, and owner as those of the packed file

uucp—copy files to another system, UNIX-to-UNIX system copy

Example Explanationuuencode mybinfile decodename > uumybinfile.tosend

The first argument, mybinfile, is the existing file to be encoded. The second argument is the name to be used for the uuencoded file, after mailing the file, and uumybinfile.tosend is the file that is sent through the mail

uuencode uumybinfile.tosend

This decodes the uuencoded file and creates a filename which was given as the second argument to uuencode

uuencode—uuencode, uudecode—encode a binary file into ASCII text in order to send it through e-mail, or convert it back into its original form

Example Explanationuuencode mybinfile decodedname > uumybinfile.tosend

The first argument, mybinfile, is the existing file to be encoded. The second argument is the name to be used for the uuencoded file, after mailing the file, and uumybinfile.tosend is sent through the mail

uucode uumybinfile.tosend

This decodes the uuencoded file and creates a filename which was given as the second argument to uuencode

wc—counts lines, words, and characters

Example Explanationwc filex Prints the number of

lines, words, and characters in filex.

who | wc –l The output of the who command is piped to wc, displaying the number of lines counted

wc –l filex Prints the number of line in filex

what—extracts SCCS version information from a file by printing information found after the @(#) pattern

What searches each filename for the occurrence of the pattern, @(#), that the SCCS get command substitutes for the %Z% keyword, and prints what follows up to a “>, new line, \, or null character

which(UCB)—locates a command and displays its pathname or alias

which takes a list of names and looks for the files that would be executed had the names been given as commands. Each argument is expanded if it is aliased, and searched for along the user’s path. Both alias and path are taken from the user’s .cshrc file. Only .cshrc is used

whereis(UCB)—locates the binary, source, and manual page file for a command

who—displays who is logged on the system

Example Explanation

who Displays the users logged on the system

who ami Displays information about the current user

write—writes a message to another user

Writes copies to lines from your terminal to another’s terminal

xargs—constructs an argument list(s) and executes a command

Example Explanationls $1 | xargs –i –t mv ${} $2/{}

Moves all files from directory $1 to directory $2, and echoes each mv command just before executing

ls | xargs –p –l rm –rf Prompts (-p) the user files are to be removed at a time and removes each one

zcat—uncompress a compressed file to standard output. Same as uncopmress -c

Example Explanationzcat book.doc.Z | more

Uncompress books.doc.Z and pipes the output to more

References UNIX SHELLS BY EXAMPLE BY ELLIE

QUIGLEY UNIX FOR PROGRAMMERS AND

USERS BY G. GLASS AND K ABLES UNIX SHELL PROGRAMMING BY S.

KOCHAN AND P. WOOD