Shulou(Shulou.com)06/01 Report--

Summary of grammar knowledge points of bash script programming the second part

Undertake the first part of the summary and analysis.

Interactive programming of 6.bash programming

Read

-p "prompt" / / prompt

-ttimeout

Give a default value to a variable

VarName=$ {varName:-value}

If varName is not empty, the value of varName is returned; otherwise varName will use value as its value

Using the read parameter [- p] allows [- p] to be followed by a string and n shell variables after the string. N shell variables are used to receive strings input from the shell interface

Usage: read-p "string" var1 var2... Varn

Exercise: determine the content type of a file by giving the path to a file on the keyboard

#! / bin/bash

Read-p "Enter a file name:" fileName

Type $fileName

The content type of the file under the directory is determined by a path given by the keyboard, which defaults to /.

For example, enter a user name and return its shell

#! / bin/bash

#

Read-p "Plz input a username:" userName

Ifid $userName & > / dev/null; then

Echo "The shell of $userName is `grep" ^ $userName\ > "/ etc/passwd | cut-d:-f7`."

Else

Echo "No such user. Stupid."

Fi

Example: a menu is displayed to the user as follows:

Cpu) show cpu infomation

Mem) show memory infomation

*) quit

1. If the user selects cpu, the contents of the / proc/cpuinfo file are displayed

2. If the user selects mem, the contents of the / proc/meminfo file are displayed

3. Quit

#! / bin/bash

#

Echo "- menu-"

Echo "cpu) show cpu infomation"

Echo "mem) show memory infomation"

Echo "*) quit"

Echo "- menu-"

Read-p "Plz give your choice:" choice

If ["$choice" = = 'cpu']; then

Cat / proc/cpuinfo

Elif ["$choice" = = 'mem']; then

Cat / proc/meminfo

Else

Echo "Quit"

Exit 3

Fi

No newlines, tabs, or spaces before the second EOF

#! / bin/bash

#

Cat / dev/null

[$?-eq 0] & & echo "Stop $srvName OK" & & return 0

Else

Echo "$srvName is not started."

Return 1

Fi

}

Status () {

If [- f $lockFile]; then

Echo "$srvName is running."

Else

Echo "$srvName is stopped."

Fi

Return 0

}

Usage () {

Echo "Usage:$srvName {start | stop | restart | status}"

Return 0

}

Case $1 in

Start)

Start

Stop)

Stop

Restart)

Stop

Start

Status)

Status

*)

Usage

Exit 1

Esac

Exercise: write a script to perform the following functions (using functions):

1. Prompt the user for an executable command

2. Get all the library files on which this command depends (using the ldd command)

3. Copy the command to the directory corresponding to / mnt/sysroot/

Explanation: suppose that if you copy the cat command and its executable path is / bin/cat, then copy / bin/cat to the / mnt/sysroot/bin/ directory. If you copy the useradd command and the executable path of useradd is / usr/sbin/useradd, copy it to the / mnt/sysroot/usr/sbin/ directory.

4. Copy the library files to the corresponding directory of / mnt/sysroot/

#! / bin/bash

#

Target=/mnt/sysroot/

[- d $target] | | mkdir $target

PreCommand () {

If which $1 & > / dev/null; then

CommandPath= `which-- skip-alias $1`

Return0

Else

Echo "No such command."

Return1

Fi

}

CommandCopy () {

CommandDir= `dirname $1`

[- d ${target} ${commandDir}] | | mkdir-p ${target} ${commandDir}

[- f ${target} ${commandPath}] | | cp $1 ${target} ${commandDir}

}

LibCopy () {

For lib in `ldd $1 | egrep-o "/ [^ [: space:]] +" `; do

LibDir= `dirname $lib`

[- d$ {target} ${libDir}] | | mkdir-p ${target} ${libDir}

[- f ${target} ${lib}] | | cp $lib ${target} ${libDir}

Done

}

Read-p "Plz enter a command:" command

Until ["$command" = = 'quit']; do

If preCommand $command & > / dev/null; then

CommandCopy $commandPath

LibCopy $commandPath

Fi

Read-p "Plz enter a command:" command

Done

Signal capture in 8.bash programming

Signal type

1) SIGHUP this signal is sent at the end of the user terminal connection (normal or abnormal), usually when the terminal control process ends, notifying each job in the same session, then they are no longer associated with the control terminal.

2) SIGINT program termination (interrupt) signal, which is sent when the user types an INTR character (usually Ctrl-C)

3) SIGQUIT is similar to SIGINT, but is controlled by QUIT characters (usually Ctrl-/). The process generates a core file when it receives a SIGQUIT exit, which in this sense 1 is similar to a program error signal.

4) SIGILL executed illegal instructions, usually because of an error in the executable itself or an attempt to execute a data segment. This signal may also be generated when the stack is overflowed.

The trap command is used to capture a signal in a shell program, after which you can react in three ways:

(1) execute a program to process the signal

(2) default operation of accepting signals

(3) ignore this signal

Trap provides three basic forms for the above three ways:

The first form of trap command executes the command string in double quotes when shell receives a signal with the same value in the signallist list.

Trap 'commands' signal-list

Trap "commands" signal-list

The second form of trap command restores the default operation of the signal: trap signal-list

The third form of trap command allows you to ignore the signal: trap "" signal-list

Trap 'COMMAND' SIGINT (for shutting down the process)

Example: write a script that can ping to detect whether all hosts in the specified network are online, and can receive ctrl+c commands to exit when the execution is not finished.

#! / bin/bash

QuitScript () {

Echo "Quit..."

}

Trap 'quitScript; exit 5' SIGINT

CnetPing () {

For i in {1... 254}; do

If ping-c 1-W 1 $1.Secreti & > / dev/null; then

Echo "$1.Secreti is up."

Else

Echo "$1.Secreti is down."

Fi

Done

}

BnetPing () {

For j in {0.255}; do

CnetPing $1.10j

Done

}

AnetPing () {

For m in {0.255}; do

BnetPing $1.millim

Done

}

NetType= `echo $1 | cut-d "."-f1`

If [$netType-ge 1-a $netType-le 126]; then

AnetPing $netType

Elif [$netType-ge 128-a $netType-le 191]; then

BnetPing $(echo $1 | cut-dwelling.'- F1 Magi 2)

Elif [$netType-ge 192-a $netType-le 223]; then

CnetPing $(echo $1 | cut-dudes.'- F1-3)

Else

Echo "Wrong"

Exit 2

Fi

Array 9.1 Array definition for 9.bash programming

Array: multiple consecutive independent memory spaces, each equivalent to a variable

Array elements: array name + index (numbered from 0)

The representation of the index:

Digital index: a [index]

A [0], a [1]

Associative array of bash 4.0s

A [hello], a [hi]

Declaration array: declare-an ARRAR_NAME

Associative array: declare-An ARRAY_NAME

Support for sparse formats: only one-dimensional arrays

Array assignment:

(1) assign values to one element at a time:

A [0] = $RANDOM

...

Echo ${a [0]}

(2) assign values to all elements at once:

A = (red blue yellowgreen)

A pair of parentheses indicates an array, and the array elements are separated by a "space" symbol.

(3) assign values by index:

A = ([0] = green [3] = red [2] = blue [6] = yellow)

(4) replace the command:

Logs= ($(ls / var/log/*.log))

Or logs= (/ var/log/*.log)

Echo ${logs [0]}

(5) user input

Read-an ARRAY

Array access:

Access with index: array [index]

Length of the array:

${# ARRAY [*]}

${# ARRAY [@]}

Eg:echo ${# test [*]}

Echo ${# test [@]}

Exercise: write a script to generate 10 random numbers, save them to an array, and then display the elements marked as even in the array

#! / bin/bash

For i in {0.. 9}; do

Num [$I] = $RANDOM

If [$[$I% 2]-eq 0]; then

Echo "a [I] is$ {a [I]}"

Fi

Done

To select an element from an array:

${ARRAY [@]: offset:number}

Slice:

Offset: number of elements offset

Number: the number of elements taken out

${ARRAY [@]: offset}: all elements after the offset is taken out

${ARRAY [@]}: take out all elements

Array replication:

To use ${ARRAY [@]}

$@: each parameter is a separate string

$*: all parameters are a string

Append elements to an array: non-sparse format

Mylogs

Mylogs [${# week [@]}]

Example: copy the even-numbered elements of an array to a new array

#! / bin/bash

Declare-a mylogs

Logs= (/ var/log/*.log)

Echo ${logs [@]}

For i in `seq 0 ${# logs [@]} `; do

If [$[$I% 2]-eq 0]; then

Index=$ {# mylogs [@]}

Mylogs [$index] = ${logs [$I]}

Fi

Done

Echo ${mylogs [@]}

Remove the element from the array: unset ARRAY [index]

Exercise 1: generate 10 random numbers and sort them in ascending order

#! / bin/bash

For ((ionometry1))

Do

For ((jumb0witj

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.