Copyright Sams Teach Yourself Shell Programming in 24 Hours

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SEE ALSO w(1), who(1), whodo(1M), attributes(5) NOTES who -b gives the time the system was last booted. As you can see this man page is divided into several sections. These sections are described in Table 2.1. Table 2.1 Sections in a Man Page Section Description NAME This section gives the name of the command along with a short description of the command. SYNOPSIS This section describes all the different modes in which the command can be run. If a command accepts arguments they are shown in this section. DESCRIPTION This section includes a verbose description of the command. If a command accepts arguments, each argument will be fully explained in this section EXAMPLE This section usually shows you how to execute a command, along with some sample output. SEE ALSO This section lists other commands that are related to this command. NOTES This section usually lists some additional information about the command. Sometimes it lists known bugs with a particular command. Most man pages include all the sections given in Table 2.1 and might include one or two optional sections described in Table 2.2. Table 2.2 Optional Sections Found in Man Pages Section Description AVAILABILITY This section describes the versions of UNIX that include support for a given command. Sometimes it lists the optional software packages you need to purchase from the vendor to gain extra functionality from a command. KNOWN BUGS This section usually lists one or more known problems with a command. If you encounter a problem that is not included in this section, you should report it to your UNIX vendor. FILES This section lists the files that are required for a command to function correctly. It might also list the files that can be used to configure a command. AUTHORS or CONTACTS These sections list the command's authors or provide some contact information regarding a command. STANDARDS COMPLIANCE Some commands have behavior that is specified by a standards organization such as ISO (International Standards Organization), IEEE (Institute of Electrical and Electronic Engineers), or ANSI (American National Standards Institute). This section lists the standards with which a particular command complies.
Try using the man command to get more information on some of the commands I have discussed in this chapter. If the man command cannot find a man page corresponding to the command you requested, it issues an error message. For example, the command $ man apple produces an error message similar to the following on my system: No manual entry for apple The exact error message depends on your version of UNIX. Manual Sections The term manual page comes from the original versions of UNIX, when the online pages were available as large bound manuals. In all, there were eight different manuals covering the main topics of the UNIX system. These manuals are described in Table 2.3. Table 2.3 The UNIX System Manuals Manual Section Description 1 Covers commands. 2 Covers UNIX system calls. System calls are used inside a program, such as date, to ask the kernel for a service. 3 Covers libraries. Libraries are used to store non-kernel-related functions used by C programmers. 4 Covers file formats. This manual specifies the format of files such as /etc/passwd. 5 Also covers file formats. 6 Includes the instructions for playing the games that came with UNIX. 7 Covers device drivers. 8 Covers system maintenance. Unlike the printed version, where you had to know the section where you needed to look for a particular manual page, the man command looks in all the sections for the information you requested. This makes it much easier to get help using the man pages. Sams Teach Yourself Shell Programming in 24 Hours Contents Index Hour 2: Script Basics Sections in this Chapter: Previous Chapter Next Chapter The UNIX System Summary Shell Initialization Questions Getting Help Terms Previous Section Next Section
Page 1 and 2: Sams Teach Yourself Shell Programmi
Page 3 and 4: ● Using Single Quotes ● Using D
Page 5 and 6: ● Questions Hour 20: Debugging
Page 9 and 10: ● Part I is an introduction to UN
Page 11 and 12: Many of the examples and the answer
Page 17 and 18: $ date [ENTER] Wed Dec 9 08:49:13 P
Page 19 and 20: anga pts/0 Dec 9 08:49 $ Here, the
Page 23 and 24: The original UNIX shell was written
Page 25 and 26: There are three major versions of k
Page 31 and 32: example, when you execute the comma
Page 35 and 36: This executes the compound command
Page 37 and 38: chmod a+x ./logins Here you are usi
Page 39: Sams Teach Yourself Shell Programmi
Page 49 and 50: Hidden Files So far you have used l
Page 51 and 52: © Copyright Macmillan Computer Pub
Page 53 and 54: Numbering Lines The cat command als
Page 55 and 56: command $ wc -w .rhosts produces th
Page 59 and 60: produces the following error: cp: w
Page 61 and 62: m: work directory The two files are
Page 67 and 68: name. Thus both of the following fi
Page 69 and 70: ../docs/ch5.doc represents the file
Page 71 and 72: changes to the directory /usr/local
Page 75 and 76: If you specify several arguments in
Page 77 and 78: Sometimes when you want to create a
Page 79 and 80: $ cp -r docs /mnt/zip/backup cp: ca
Page 81 and 82: Removing Directories You can use tw
Page 87 and 88: $ ls -ld /home/ranga This produces
Page 89 and 90: You can see the relative path by us
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Sections in this Chapter: File Type
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The permission block for this file
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Here, expression is a statement of
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For example, if the directory pub c
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Restrictions The super user, root,
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Sams Teach Yourself Shell Programmi
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Running the same ls command as in t
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Tip - Background Processes That Wri
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the fg command. By default, the pro
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dhorvath 6770 3662 2 10:35:45 pts/6
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By default, a process runs with the
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Process Identifier --The process id
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Variable Names The name of a variab
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Array Variables The Bourne shell, s
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$ band[2]=mike $ band[3]=gene Tip -
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Hour 7: Variables Sections in this
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uses internally. Users can modify t
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Here, command is the name of a comm
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$ ls ch??.doc to accomplish this. M
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© Copyright Macmillan Computer Pub
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is unset. Assigning a Default Value
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© Copyright Macmillan Computer Pub
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It now gives this error result: Hel
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Sections in this Chapter: Quoting w
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To the shell, one or more spaces or
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Quoting Regular Expression Wildcard
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fi list5 Both the elif and the else
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Here you have an elif statement tha
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Consider the following if statement
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If you were to use the - n option i
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else echo "An error was encountered
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1. First the test [ -z "$DTHOME" ]
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esac Here the string contained in $
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The execution of a while loop proce
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5 4 3 2 1 0 6 5 4 3 2 1 0 7 6 5 4 3
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2. If the exit status of command is
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for i in 0 1 2 3 4 5 6 7 8 9 do ech
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3. When the user enters a value, $R
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The continue Command The continue c
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If you want to list the contents of
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In this version, the basename comma
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USAGE="Usage: ´basename $0´ [-c|-
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uuencoding a file. For readers who
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fi fi echo $MSG You could simplify
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● Formatting escape sequences Emb
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Name User Name Sriranga ranga Sriva
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Table 13.2 Formatting Sequence Type
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printf "%-32s " "$i" if [ -d "$i" ]
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anga ttyp0 Oct 27 19:42 (:0.0) amma
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Say you need to send a list of phon
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"Miscellaneous Tools," I will show
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$ exec 4>fd4.out associates the fil
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command > file 2>&1 list > file 2>&
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when the while loop exits, the valu
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Note - The shell uses the value of
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This function has three important p
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} OLDIFS="$IFS" IFS=: # print each
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} # set the directory to pop to the
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index.html RCS humor misc downloads
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unix has several additional pieces
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pqops.c:/* Function to delete a nod
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Here I specified set2 as the space
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$ tr '!?":;\[\]{}(),.\t\n' ' ' < /h
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in 69 ' 65 the 389 to 164 of 127 No
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tr '[:classname:]' 'set2' Here clas
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single letters, whereas in awk the
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able was I, ere I saw elba Because
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By adding the ^ metacharacter as fo
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\$[0-9]*\.[0-9][0-9]\/[a-zA-Z]*/ If
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Here you list the name of a fruit a
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$ rm fruit_prices.txt.$$ Performing
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Fortunately, the s command provides
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lrwxrwxrwx 1 ranga users 8 Nov 27 1
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The original awk has remained almos
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Kiwi 22 Pineapple 35 Apple 78 All t
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Pineapple $1.29 35 REORDER Apple $0
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$ ls -l produces output formatted s
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The value that you assign a variabl
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x=x+1 In awk this can be written in
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the pattern specifies. To solve you
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awk -F: '{ ... }' The major differe
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identical to expressions you looked
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The basic syntax is do { actions }
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B:amount Here amount is the balance
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The OUTPUT variable contains the >
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: ${LINES:=24} ${TERM:?"TERM not se
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Sections in this Chapter: The eval
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eports/1998 The starting directory.
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find: -type Option The -type option
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find / -name alpha -size +50 -mtime
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18 quit $ obase=16 sets the output
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The default action for the signals
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fi Init() { printf "INFO: Initializ
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4. Wait for the program to finish e
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} if [ $? -eq 0 ] ; then echo "Sub-
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A third way of enabling debugging i
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Here the debugging mode is enabled
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if [ $YN = "y" ] ; then Making this
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$ /bin/sh -nv ./buggy2.sh the outpu
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Deleting old backups, please wait..
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If you do not type a response and p
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To deactivate debugging, use either
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3 MSG="hello" 4 echo_error $MSG Her
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echo "ERROR: File $MYFILE was not f
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previous call to this function. Aft
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} Before you look at some examples
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dev/hda1 1190014 664661 463867 59%
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The number returned is in kilobytes
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getUID() { id $1 | sed -e 's/(.*$//
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63 printf "$1 (y/n)? " 64 65 if [ -
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}' 171 # Args: $1 -> the command na
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Some UNIX versions implement a work
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24 printERROR "The source $1 is not
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easily modify the script to replace
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Hour 22: Problem Solving with Shell
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To maintain your address book, you
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produces two matches: Name: Srirang
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26 # enable erasing input 27 28 stt
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2. Based on user feedback, delete t
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73 promptYESNO "Delete this entry"
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MYADDRESSBOOK="$HOME/addressbook" i
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Here, options is one or more of the
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Now that you have looked at using t
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Abstraction is a technique used to
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warning: '-' deprecated; use 'ps au
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produce the same result if the curr
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The structure of the UNIX directory
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OLDPREFIX=aaa NEWPREFIX=bbb for FIL
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history (Korn/Bash) shows the most
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Sections in this Chapter: Reserved
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^ bitwise exclusive OR operation |
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Bash array initialization USERVAR=(
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order to fix problems. default beha
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minor number UNIX uses this to asso
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important parameters. This is usual
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Sections in this Chapter: Chapter 1
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USAGE="Usage: ´basename $0´ [-v]
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Appendix C: Quiz Answers Sections i
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awk -F: ' $1 == "B" { BAL=$NF ; nex
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} if [ $DEF_TOUT -ne 0 ] ; then sle
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Sections in this Chapter: Chapter 1
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} fi if [ ! -d "$1" ] ; then printE
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numeric variables, 1st pattern-spec
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wildcards, 1st Bourne shells. See s
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(colon), 1st character, 1st, 2nd, 3
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grep, 1st, 2nd line numbers, 1st li
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stty addperson script, 1st tail, 1s
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emoving temporary files, 1st displa
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mv command, 1st, 2nd rmdir command,
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interactive mode, 1st multiple inpu
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starting directory, 1st, 2nd findin
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installation scripts disk usage, 1s
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eak command, 1st, 2nd, 3rd continue
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mvdir.sh, 1st, 2nd, 3rd, 4th, 5th,
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edirection, 1st, 2nd appending to f
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[0-9]*, 1st percent sign (%) job nu
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profiles shell specific startup wit
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hardware type, 1st, 2nd improving,
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(standard error), 1st displaying me
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prompt, 1st, 2nd, 3rd, 4th quoting
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egp command, 1st -k option sort com
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