Linux shell編程入門

時間 2019-11-08

標籤 linux shell 編程入門欄目 Linux 简体版

原文原文鏈接

#!/bin/bashhtml

echo "前進程號:"$$java

echo "start"mysql

sleep 10linux

kill $$git

sleep 900000000redis

echo "end"sql

[root@weekend110 shell]# cat for.sh shell

#!/bin/bashapache

for ((i=0;i<10;i++))編程

echo $i

done

[root@weekend110 shell]# for.sh

[root@weekend110 shell]#

[root@weekend110 shell]# more for1.sh

#!/bin/bash

for i in 0 1 2 3 4 5 6 7 8 9

echo $i

done

[root@weekend110 shell]# for1.sh

[root@weekend110 shell]#

[root@weekend110 shell]# more for2.sh

#!/bin/bash

for i in {0..9}

echo $i

done

[root@weekend110 shell]# for2.sh

[root@weekend110 shell]#

[root@weekend110 shell]# more while.sh

#!/bin/bash

while [ $1 -gt 2 ]

echo "true"

sleep 1

done

[root@weekend110 shell]#

[root@weekend110 shell]# more until.sh

#!/bin/bash

until [ $1 -gt 2 ]

echo "true"

sleep 1

done

[root@weekend110 shell]#

[root@weekend110 shell]# more if.sh

#!/bin/bash

if [ $1 -eq 1 ]

then

echo 'one'

else

echo 'none'

[root@weekend110 shell]# more if1.sh

#!/bin/bash

if [ $1 -eq 1 ]

then

echo 'one'

elif [ $1 -eq 2 ]

then

echo 'two'

elif [ $1 -eq 3 ]

then

echo 'three'

else

echo 'none'

[root@weekend110 shell]#

[root@weekend110 shell]# more case.sh

#!/bin/bash

case $1 in

echo 'one'

;;

echo 'two'

;;

echo 'three'

;;

echo 'none'

;;

esac

[root@weekend110 shell]# case.sh

none

[root@weekend110 shell]#

這裏，我就在，/下新建shell目錄，用來做爲shell編程的入門。

[root@weekend110 /]# ls

bin data etc lib lost+found misc net proc sbin srv tmp var

boot dev home lib64 media mnt opt root selinux sys usr

[root@weekend110 /]# mkdir shell

[root@weekend110 /]# ls

bin data etc lib lost+found misc net proc sbin shell sys usr

boot dev home lib64 media mnt opt root selinux srv tmp var

[root@weekend110 /]# cd shell/

[root@weekend110 shell]# ll

total 0

[root@weekend110 shell]#

[root@weekend110 shell]# ls

[root@weekend110 shell]# vim break1.sh

[root@weekend110 shell]# ll

total 4

-rw-r--r--. 1 root root 79 Oct 22 09:15 break1.sh

[root@weekend110 shell]# chmod +x break1.sh

[root@weekend110 shell]# ll

total 4

-rwxr-xr-x. 1 root root 79 Oct 22 09:15 break1.sh

[root@weekend110 shell]# cat break1.sh //若是變量i達到2，就跳出循環

#!/bin/bash

for ((i=0;i<10;i++))

if [ $i -eq 2 ]

then

break

echo $i

done

[root@weekend110 shell]# break1.sh

-bash: break1.sh: command not found

[root@weekend110 shell]# ./break1.sh 由於，此刻，還沒加入到環境變量

[root@weekend110 shell]#

[root@weekend110 shell]# pwd

/shell

[root@weekend110 shell]# vim /etc/profile

export PATH=$PATH:/shell/

[root@weekend110 shell]# source /etc/profile

[root@weekend110 shell]# break1.sh

[root@weekend110 shell]#

這樣，就達到了。

如今，寫，while循環在外，for循環在內。

[root@weekend110 shell]# ls

break1.sh break2.sh

[root@weekend110 shell]# cat break2.sh

#!/bin/bash

while [ 1 -eq 1 ]

for ((i=0;i<10;i++))

if [ $i -eq 2 ]

then

break

echo $i

done

echo 'yes'

sleep 1

done

[root@weekend110 shell]# break2.sh

yes

[root@weekend110 shell]#

[root@weekend110 shell]# cat break3.sh

#!/bin/bash

while [ 1 -eq 1 ]

for ((i=0;i<10;i++))

if [ $i -eq 2 ]

then

break 2 //在這裏，默認是1，寫個2，則說的是跳出2層循環。

echo $i

done

echo 'yes'

sleep 1

done

[root@weekend110 shell]# break3.sh

[root@weekend110 shell]#

跳出單循環

for((i=0;i<10;i++))

echo $i

if [ $i -eq 2 ]

then

break

done

跳出內循環

while [ 1 -eq 1 ]

echo 'yes'

sleep 1

for((i=0;i<10;i++))

echo $i

if [ $i -eq 2 ]

then

break

done

跳出外循環

while [ 1 -eq 1 ]

echo 'yes'

sleep 1

for((i=0;i<10;i++))

echo $i

if [ $i -eq 2 ]

then

break 2

done

[root@weekend110 shell]# cat continue.sh

#/bin/bash

for ((i=0;i<10;i++))

if [ $i -eq 2 ]

then

continue

echo $i

done

[root@weekend110 shell]# continue.sh

[root@weekend110 shell]#

[root@weekend110 shell]# cat fun.sh

#!/bin/bash

function test(){

echo "this is a funcction"

}

[root@weekend110 shell]# fun.sh

[root@weekend110 shell]# cat fun.sh

#!/bin/bash

function test(){

echo "this is a funcction"

}

test

[root@weekend110 shell]# fun.sh

this is a funcction

[root@weekend110 shell]#

可是，通常，生產裏，也不會這麼去作。

[root@weekend110 shell]# cat fun.sh

#!/bin/bash

function test(){

echo "this is a funcction"

}

[root@weekend110 shell]# cat funtest.sh

#!/bin/bash

source fun.sh

test

[root@weekend110 shell]# funtest.sh

this is a funcction

[root@weekend110 shell]#

這樣的好處，是fun.sh腳本，能夠重用。

[root@weekend110 shell]# cat fun.sh

#!/bin/bash

function test(){

echo "this is a funcction"$1

}

[root@weekend110 shell]# cat funtest.sh

#!/bin/bash

source fun.sh

test haha

[root@weekend110 shell]# funtest.sh

this is a funcctionhaha

[root@weekend110 shell]#

[root@weekend110 shell]# cat fun.sh

#!/bin/bash

function test(){

echo "this is a funcction"$1

}

[root@weekend110 shell]# cat funtest.sh

#!/bin/bash

source fun.sh

test $1

[root@weekend110 shell]# funtest.sh

this is a funcction

[root@weekend110 shell]# funtest.sh hehe

this is a funcctionhehe

[root@weekend110 shell]# funtest.sh haha hehe

this is a funcctionhaha

[root@weekend110 shell]# funtest.sh hahahehe

this is a funcctionhahahehe

[root@weekend110 shell]#

[root@weekend110 shell]# cat fun.sh

#!/bin/bash

function test(){

echo "this is a funcction"$1

return 20

}

[root@weekend110 shell]# cat funtest.sh

#!/bin/bash

source fun.sh

test $1

[root@weekend110 shell]# funtest.sh haha

this is a funcctionhaha

[root@weekend110 shell]# echo $?

[root@weekend110 shell]#

[root@weekend110 shell]# type cd

cd is a shell builtin

[root@weekend110 shell]# type date

date is hashed (/bin/date)

[root@weekend110 shell]#

[root@weekend110 shell]# help cd

cd: cd [-L|-P] [dir]

Change the shell working directory.

Change the current directory to DIR. The default DIR is the value of the

HOME shell variable.

The variable CDPATH defines the search path for the directory containing

DIR. Alternative directory names in CDPATH are separated by a colon (:).

A null directory name is the same as the current directory. If DIR begins

with a slash (/), then CDPATH is not used.

If the directory is not found, and the shell option `cdable_vars' is set,

the word is assumed to be a variable name. If that variable has a value,

its value is used for DIR.

Options:

-L force symbolic links to be followed

-P use the physical directory structure without following symbolic

links

The default is to follow symbolic links, as if `-L' were specified.

Exit Status:

Returns 0 if the directory is changed; non-zero otherwise.

[root@weekend110 shell]#

[root@weekend110 shell]# man date 按長空格鍵，翻頁

DATE(1) User Commands DATE(1)

NAME

date - print or set the system date and time

SYNOPSIS

date [OPTION]... [+FORMAT]

date [-u|--utc|--universal] [MMDDhhmm[[CC]YY][.ss]]

DESCRIPTION

Display the current time in the given FORMAT, or set the system date.

-d, --date=STRING

display time described by STRING, not ‘now’

-f, --file=DATEFILE

like --date once for each line of DATEFILE

-r, --reference=FILE

display the last modification time of FILE

-R, --rfc-2822

output date and time in RFC 2822 format. Example: Mon, 07 Aug 2006 12:34:56 -0600

--rfc-3339=TIMESPEC

output date and time in RFC 3339 format. TIMESPEC=‘date’, ‘seconds’, or ‘ns’ for date and time to the

indicated precision. Date and time components are separated by a single space: 2006-08-07 12:34:56-06:00

-s, --set=STRING

set time described by STRING

-u, --utc, --universal

print or set Coordinated Universal Time

--help display this help and exit

[root@weekend110 shell]# type date

date is hashed (/bin/date)

[root@weekend110 shell]# man date

DATE(1) User Commands DATE(1)

NAME

date - print or set the system date and time

SYNOPSIS

date [OPTION]... [+FORMAT]

date [-u|--utc|--universal] [MMDDhhmm[[CC]YY][.ss]]

DESCRIPTION

Display the current time in the given FORMAT, or set the system date.

-d, --date=STRING

display time described by STRING, not ‘now’

-f, --file=DATEFILE

like --date once for each line of DATEFILE

-r, --reference=FILE

display the last modification time of FILE

-R, --rfc-2822

output date and time in RFC 2822 format. Example: Mon, 07 Aug 2006 12:34:56 -0600

--rfc-3339=TIMESPEC

output date and time in RFC 3339 format. TIMESPEC=‘date’, ‘seconds’, or ‘ns’ for date and time to the

indicated precision. Date and time components are separated by a single space: 2006-08-07 12:34:56-06:00

-s, --set=STRING

set time described by STRING

-u, --utc, --universal

print or set Coordinated Universal Time

--help display this help and exit

--version

output version information and exit

FORMAT controls the output. Interpreted sequences are:

%% a literal %

%a locale’s abbreviated weekday name (e.g., Sun)

%A locale’s full weekday name (e.g., Sunday)

%b locale’s abbreviated month name (e.g., Jan)

%B locale’s full month name (e.g., January)

%c locale’s date and time (e.g., Thu Mar 3 23:05:25 2005)

%C century; like %Y, except omit last two digits (e.g., 20)

%d day of month (e.g, 01)

%D date; same as %m/%d/%y

%e day of month, space padded; same as %_d

%F full date; same as %Y-%m-%d

%g last two digits of year of ISO week number (see %G)

%G year of ISO week number (see %V); normally useful only with %V

%h same as %b

%H hour (00..23)

%I hour (01..12)

%j day of year (001..366)

%k hour ( 0..23)

%l hour ( 1..12)

%m month (01..12)

%M minute (00..59)

%n a newline

%N nanoseconds (000000000..999999999)

%p locale’s equivalent of either AM or PM; blank if not known

%P like %p, but lower case

%r locale’s 12-hour clock time (e.g., 11:11:04 PM)

%R 24-hour hour and minute; same as %H:%M

%s seconds since 1970-01-01 00:00:00 UTC

%S second (00..60)

%t a tab

%T time; same as %H:%M:%S

%u day of week (1..7); 1 is Monday

%U week number of year, with Sunday as first day of week (00..53)

%V ISO week number, with Monday as first day of week (01..53)

%w day of week (0..6); 0 is Sunday

%W week number of year, with Monday as first day of week (00..53)

%x locale’s date representation (e.g., 12/31/99)

%X locale’s time representation (e.g., 23:13:48)

%y last two digits of year (00..99)

%Y year

%z +hhmm numeric timezone (e.g., -0400)

%:z +hh:mm numeric timezone (e.g., -04:00)

%::z +hh:mm:ss numeric time zone (e.g., -04:00:00)

%:::z numeric time zone with : to necessary precision (e.g., -04, +05:30)

%Z alphabetic time zone abbreviation (e.g., EDT)

By default, date pads numeric fields with zeroes. The following optional flags may follow ‘%’:

- (hyphen) do not pad the field

_ (underscore) pad with spaces

0 (zero) pad with zeros

^ use upper case if possible

# use opposite case if possible

After any flags comes an optional field width, as a decimal number; then an optional modifier, which is either E

to use the locale’s alternate representations if available, or O to use the locale’s alternate numeric symbols

if available.

DATE STRING

The --date=STRING is a mostly free format human readable date string such as "Sun, 29 Feb 2004 16:21:42 -0800"

or "2004-02-29 16:21:42" or even "next Thursday". A date string may contain items indicating calendar date,

time of day, time zone, day of week, relative time, relative date, and numbers. An empty string indicates the

beginning of the day. The date string format is more complex than is easily documented here but is fully

described in the info documentation.

ENVIRONMENT

TZ Specifies the timezone, unless overridden by command line parameters. If neither is specified, the set-

ting from /etc/localtime is used.

AUTHOR

Written by David MacKenzie.

REPORTING BUGS

Report date bugs to bug-coreutils@gnu.org

GNU coreutils home page: <http://www.gnu.org/software/coreutils/>

General help using GNU software: <http://www.gnu.org/gethelp/>

Report date translation bugs to <http://translationproject.org/team/>

<http://gnu.org/licenses/gpl.html>.

This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permit-

ted by law.

1 storm基本概念 + storm編程規範及demo編寫

在這裏，爲何像這的第三方，爲何不需加nohup呢?那是由於，它們在開發時，源碼、內核和腳本都弄好了。

本身寫腳本，須要加nohup。

　　問：使用nohup啓動的java進程，可讓java日誌不打入到nohup.out中，而打到本身制定的日誌文件中麼？

答:不能夠，必須是在nohup.out。在shell裏面，寫，是能夠打人到本身制定的日誌文件中。

標準輸入、標準輸出、標準錯誤輸出

標準輸入

[root@weekend110 shell]# more a.txt

a s

vv a

[root@weekend110 shell]# wc < a.txt 把a.txt當作標準輸入，傳給wc

3 5 12 3行，5個單詞，12個字節數

標準輸出

[root@weekend110 shell]# ls

arr1.sh arr2.sh a.txt break1.sh break2.sh break3.sh continue.sh fun.sh funtest.sh nohup.out sleep.sh zookeeper.out

[root@weekend110 shell]# ls > a.txt 把ls當作標準輸出，傳給a.txt

[root@weekend110 shell]# more a.txt

arr1.sh

arr2.sh

a.txt

break1.sh

break2.sh

break3.sh

continue.sh

fun.sh

funtest.sh

nohup.out

sleep.sh

zookeeper.out

[root@weekend110 shell]# ls > a.txt 覆蓋

[root@weekend110 shell]# more a.txt

arr1.sh

arr2.sh

a.txt

break1.sh

break2.sh

break3.sh

continue.sh

fun.sh

funtest.sh

nohup.out

sleep.sh

zookeeper.out

[root@weekend110 shell]# ls 1> a.txt 等價於 ls > a.txt

[root@weekend110 shell]# more a.txt

arr1.sh

arr2.sh

a.txt

break1.sh

break2.sh

break3.sh

continue.sh

fun.sh

funtest.sh

nohup.out

sleep.sh

zookeeper.out

[root@weekend110 shell]# ls >> a.txt 追加

[root@weekend110 shell]# more a.txt

arr1.sh

arr2.sh

a.txt

break1.sh

break2.sh

break3.sh

continue.sh

fun.sh

funtest.sh

nohup.out

sleep.sh

zookeeper.out

arr1.sh

arr2.sh

a.txt

break1.sh

break2.sh

break3.sh

continue.sh

fun.sh

funtest.sh

nohup.out

sleep.sh

zookeeper.out

[root@weekend110 shell]# lkkkk 1> a.txt lkkkk是錯誤命令，標準輸出

-bash: lkkkk: command not found

[root@weekend110 shell]# lkkkk 2> a.txt 標準錯誤輸出

[root@weekend110 shell]# more a.txt

-bash: lkkkk: command not found

[root@weekend110 shell]# lkkkk 2>> a.txt 追加

[root@weekend110 shell]# more a.txt

-bash: lkkkk: command not found

[root@weekend110 shell]# ls 2>&1 > a.txt

[root@weekend110 shell]# more a.txt

arr1.sh

arr2.sh

a.txt

break1.sh

break2.sh

break3.sh

continue.sh

fun.sh

funtest.sh

nohup.out

sleep.sh

zookeeper.out

[root@weekend110 shell]# lkkkk 2>&1 >a.txt

-bash: lkkkk: command not found

[root@weekend110 shell]# lkkkk >a.txt 2>&1

[root@weekend110 shell]# more a.txt

-bash: lkkkk: command not found

[root@weekend110 shell]# lkkkk >>a.txt 2>&1

[root@weekend110 shell]# more a.txt

-bash: lkkkk: command not found

[root@weekend110 shell]# ls >>a.txt 2>&1

[root@weekend110 shell]# more a.txt

-bash: lkkkk: command not found

arr1.sh

arr2.sh

a.txt

break1.sh

break2.sh

break3.sh

continue.sh

fun.sh

funtest.sh

nohup.out

sleep.sh

zookeeper.out

[root@weekend110 shell]#

[root@weekend110 shell]# ls >/dev/null 把輸出信息定向到無底洞，即通常是把一些無用的信息，放到無底洞裏。

[root@weekend110 shell]# ls >/dev/null 2>&1

[root@weekend110 shell]# lkkkk /dev/null 2>&1

-bash: lkkkk: command not found

[root@weekend110 shell]#

[root@weekend110 shell]# more sleep.sh

#!/bin/bash

echo 'start' >>a.txt 這樣的好處，猶如在大數據裏的日誌文件同樣，便於開發人員，隨時查看日誌。就是採用這個原理

sleep 10000000000

echo 'stop'

[root@weekend110 shell]#

[root@weekend110 shell]# man crontab

CRONTAB(1) Cronie Users’ Manual CRONTAB(1)

NAME

crontab - maintain crontab files for individual users

SYNOPSIS

crontab [-u user] file

crontab [-u user] [-l | -r | -e] [-i] [-s]

DESCRIPTION

Crontab is the program used to install, remove or list the tables used to drive the cron(8) daemon. Each user

can have their own crontab, and though these are files in /var/spool/ , they are not intended to be edited

directly. For SELinux in mls mode can be even more crontabs - for each range. For more see selinux(8).

The cron jobs could be allow or disallow for different users. For classical crontab there exists cron.allow and

cron.deny files. If cron.allow file exists, then you must be listed therein in order to be allowed to use this

command. If the cron.allow file does not exist but the cron.deny file does exist, then you must not be listed

in the cron.deny file in order to use this command. If neither of these files exists, only the super user will

be allowed to use this command. The second option is using PAM authentication, where you set up users, which

could or couldn’t use crontab and also system cron jobs from /etc/cron.d/.

The temporary directory could be set in enviroment variables. If it’s not set by user than /tmp is used.

OPTIONS

-u Append the name of the user whose crontab is to be tweaked. If this option is not given, crontab exam-

ines "your" crontab, i.e., the crontab of the person executing the command. Note that su(8) can confuse

crontab and that if you are running inside of su(8) you should always use the -u option for safety’s

sake. The first form of this command is used to install a new crontab from some named file or standard

input if the pseudo-filename "-" is given.

-l The current crontab will be displayed on standard output.

-r The current crontab will be removed.

-e This option is used to edit the current crontab using the editor specified by the VISUAL or EDITOR envi-

ronment variables. After you exit from the editor, the modified crontab will be installed automatically.

ines "your" crontab, i.e., the crontab of the person executing the command. Note that su(8) can confuse

crontab and that if you are running inside of su(8) you should always use the -u option for safety’s

sake. The first form of this command is used to install a new crontab from some named file or standard

input if the pseudo-filename "-" is given.

-l The current crontab will be displayed on standard output.

-r The current crontab will be removed.

-e This option is used to edit the current crontab using the editor specified by the VISUAL or EDITOR envi-

ronment variables. After you exit from the editor, the modified crontab will be installed automatically.

-i This option modifies the -r option to prompt the user for a ’y/Y’ response before actually removing the

crontab.

-s It will append the current SELinux security context string as an MLS_LEVEL setting to the crontab file

before editing / replacement occurs - see the documentation of MLS_LEVEL in crontab(5).

SEE ALSO

crontab(5),cron(8)

FILES

/etc/cron.allow

/etc/cron.deny

STANDARDS

The crontab command conforms to IEEE Std1003.2-1992 (‘‘POSIX’’). This new command syntax differs from previous

versions of Vixie Cron, as well as from the classic SVR3 syntax.

DIAGNOSTICS

A fairly informative usage message appears if you run it with a bad command line.

AUTHOR

Paul Vixie <vixie@isc.org>

Marcela Mašláňová 20 July 2009 CRONTAB(1)

crontab對應的中文手冊：

基本格式 :

*　　*　　*　　*　　*　　command

分　時　日　月　周　命令

第1列表示分鐘1～59 每分鐘用*或者 */1表示

第2列表示小時1～23（0表示0點）

第3列表示日期1～31

第4列表示月份1～12

第5列標識號星期0～6（0表示星期天）

第6列要運行的命令

crontab文件的一些例子：

30 21 * * * /usr/local/etc/rc.d/lighttpd restart

上面的例子表示每晚的21:30重啓apache。

45 4 1,10,22 * * /usr/local/etc/rc.d/lighttpd restart

上面的例子表示每個月一、十、22日的4 : 45重啓apache。

10 1 * * 6,0 /usr/local/etc/rc.d/lighttpd restart

上面的例子表示每週6、週日的1 : 10重啓apache。

0,30 18-23 * * * /usr/local/etc/rc.d/lighttpd restart

上面的例子表示在天天18 : 00至23 : 00之間每隔30分鐘重啓apache。

0 23 * * 6 /usr/local/etc/rc.d/lighttpd restart

上面的例子表示每星期六的11 : 00 pm重啓apache。

* */1 * * * /usr/local/etc/rc.d/lighttpd restart

每一小時重啓apache

* 23-7/1 * * * /usr/local/etc/rc.d/lighttpd restart

晚上11點到早上7點之間，每隔一小時重啓apache

0 11 4 * mon-wed /usr/local/etc/rc.d/lighttpd restart

每個月的4號與每週一到週三的11點重啓apache

0 4 1 jan * /usr/local/etc/rc.d/lighttpd restart

一月一號的4點重啓apache

名稱 : crontab

使用權限 : 全部使用者

使用方式 :

crontab file [-u user]-用指定的文件替代目前的crontab。

crontab-[-u user]-用標準輸入替代目前的crontab.

crontab-1[user]-列出用戶目前的crontab.

crontab-e[user]-編輯用戶目前的crontab.

crontab-d[user]-刪除用戶目前的crontab.

crontab-c dir- 指定crontab的目錄。

crontab文件的格式：M H D m d cmd.

M: 分鐘（0-59）。

H：小時（0-23）。

D：天（1-31）。

m: 月（1-12）。

d: 一星期內的天（0~6，0爲星期天）。

cmd要運行的程序，程序被送入sh執行，這個shell只有USER,HOME,SHELL這三個環境變量

說明 :

crontab 是用來讓使用者在固定時間或固定間隔執行程序之用，換句話說，也就是相似使用者的時程表。-u user 是指設定指定

user 的時程表，這個前提是你必需要有其權限(好比說是 root)纔可以指定他人的時程表。若是不使用 -u user 的話，就是表示設

定本身的時程表。

參數 :

crontab -e : 執行文字編輯器來設定時程表，內定的文字編輯器是 VI，若是你想用別的文字編輯器，則請先設定 VISUAL 環境變數

來指定使用那個文字編輯器(好比說 setenv VISUAL joe)

crontab -r : 刪除目前的時程表

crontab -l : 列出目前的時程表

crontab file [-u user]-用指定的文件替代目前的crontab。

時程表的格式以下 :

f1 f2 f3 f4 f5 program

其中 f1 是表示分鐘，f2 表示小時，f3 表示一個月份中的第幾日，f4 表示月份，f5 表示一個星期中的第幾天。program 表示要執

行的程序。

當 f1 爲 * 時表示每分鐘都要執行 program，f2 爲 * 時表示每小時都要執行程序，其餘類推

當 f1 爲 a-b 時表示從第 a 分鐘到第 b 分鐘這段時間內要執行，f2 爲 a-b 時表示從第 a 到第 b 小時都要執行，其餘類推

當 f1 爲 */n 時表示每 n 分鐘個時間間隔執行一次，f2 爲 */n 表示每 n 小時個時間間隔執行一次，其餘類推

當 f1 爲 a, b, c,... 時表示第 a, b, c,... 分鐘要執行，f2 爲 a, b, c,... 時表示第 a, b, c...個小時要執行，其餘類推

使用者也能夠將全部的設定先存放在檔案 file 中，用 crontab file 的方式來設定時程表。

例子 :

#天天早上7點執行一次 /bin/ls :

0 7 * * * /bin/ls

在 12 月內, 天天的早上 6 點到 12 點中，每隔3個小時執行一次 /usr/bin/backup :

0 6-12/3 * 12 * /usr/bin/backup

週一到週五天天下午 5:00 寄一封信給 alex@domain.name :

0 17 * * 1-5 mail -s "hi" alex@domain.name < /tmp/maildata

每個月天天的午夜 0 點 20 分, 2 點 20 分, 4 點 20 分....執行 echo "haha"

20 0-23/2 * * * echo "haha"

注意 :

當程序在你所指定的時間執行後，系統會寄一封信給你，顯示該程序執行的內容，如果你不但願收到這樣的信，請在每一行空一格之

後加上 > /dev/null 2>&1 便可

例子2 :

#天天早上6點10分

10 6 * * * date

#每兩個小時

0 */2 * * * date

#晚上11點到早上8點之間每兩個小時，早上8點

0 23-7/2，8 * * * date

#每月的4號和每一個禮拜的禮拜一到禮拜三的早上11點

0 11 4 * mon-wed date

#1月份日早上4點

0 4 1 jan * date

範例

$crontab -l 列出用戶目前的crontab.

參考： http://www.cnblogs.com/cocowool/archive/2009/04/22/1441291.html

[root@weekend110 ~]# service crond status

crond (pid 1624) is running...

[root@weekend110 ~]# crontab -e

no crontab for root - using an empty one

#* * * * * /usr/sbin/ntpdate time.nist.gov

* * * * * echo 'date'

[root@weekend110 ~]# crontab -l　　　　　　　　查看使用

#* * * * * /usr/sbin/ntpdate time.nist.gov

* * * * * echo 'date'

[root@weekend110 ~]#

[root@weekend110 ~]# service rsyslog status

rsyslogd (pid 1244) is running...

[root@weekend110 ~]# tail -f /var/log/cron

Oct 22 20:21:44 weekend110 crontab[1891]: (root) END EDIT (root)

Oct 22 20:22:02 weekend110 CROND[1915]: (root) CMD (echo 'date')

Oct 22 20:22:25 weekend110 crontab[1923]: (root) LIST (root)

Oct 22 20:22:37 weekend110 crontab[1925]: (root) BEGIN EDIT (root)

Oct 22 20:22:41 weekend110 crontab[1925]: (root) REPLACE (root)

Oct 22 20:22:41 weekend110 crontab[1925]: (root) END EDIT (root)

Oct 22 20:22:43 weekend110 crontab[1929]: (root) LIST (root)

Oct 22 20:23:01 weekend110 crond[1624]: (root) RELOAD (/var/spool/cron/root)

Oct 22 20:23:02 weekend110 CROND[1933]: (root) CMD (echo 'date')

Oct 22 20:24:01 weekend110 CROND[1949]: (root) CMD (echo 'date')

You have new mail in /var/spool/mail/root

[root@weekend110 ~]# tail -f /var/spool/mail/root

X-Cron-Env: <SHELL=/bin/sh>

X-Cron-Env: <HOME=/root>

X-Cron-Env: <PATH=/usr/bin:/bin>

X-Cron-Env: <LOGNAME=root>

X-Cron-Env: <USER=root>

Message-Id: <20161022122502.14D1C41D08@weekend110.localdomain>

Date: Sat, 22 Oct 2016 20:25:02 +0800 (CST)

date

You have mail in /var/spool/mail/root

[root@weekend110 ~]# service crond status

crond (pid 1624) is running...

[root@weekend110 ~]#

[root@weekend110 shell]# ps

PID TTY TIME CMD

1861 pts/0 00:00:00 bash

2021 pts/0 00:00:00 ps

You have new mail in /var/spool/mail/root

[root@weekend110 shell]# jps

2023 Jps

[root@weekend110 shell]# ps -ef|grep java

root 2033 1861 0 20:29 pts/0 00:00:00 grep java

[root@weekend110 shell]# cd /tmp/hsperfdata_root/

You have new mail in /var/spool/mail/root

[root@weekend110 hsperfdata_root]# ll

total 0

[root@weekend110 hsperfdata_root]# /home/hadoop/app/zookeeper-3.4.6/bin/zkServer.sh start

JMX enabled by default

Using config: /home/hadoop/app/zookeeper-3.4.6/bin/../conf/zoo.cfg

Starting zookeeper ... STARTED

You have new mail in /var/spool/mail/root

[root@weekend110 hsperfdata_root]# jps

2075 Jps

2063 QuorumPeerMain

[root@weekend110 hsperfdata_root]# ps -ef|grep java

root 2063 1 51 20:31 pts/0 00:00:04 /home/hadoop/app/jdk1.7.0_65/bin/java -Dzookeeper.log.dir=. -Dzookeeper.root.logger=INFO,CONSOLE -cp /home/hadoop/app/zookeeper-3.4.6/bin/../build/classes:/home/hadoop/app/zookeeper-3.4.6/bin/../build/lib/*.jar:/home/hadoop/app/zookeeper-3.4.6/bin/../lib/slf4j-log4j12-1.6.1.jar:/home/hadoop/app/zookeeper-3.4.6/bin/../lib/slf4j-api-1.6.1.jar:/home/hadoop/app/zookeeper-3.4.6/bin/../lib/netty-3.7.0.Final.jar:/home/hadoop/app/zookeeper-3.4.6/bin/../lib/log4j-1.2.16.jar:/home/hadoop/app/zookeeper-3.4.6/bin/../lib/jline-0.9.94.jar:/home/hadoop/app/zookeeper-3.4.6/bin/../zookeeper-3.4.6.jar:/home/hadoop/app/zookeeper-3.4.6/bin/../src/java/lib/*.jar:/home/hadoop/app/zookeeper-3.4.6/bin/../conf: -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.local.only=false org.apache.zookeeper.server.quorum.QuorumPeerMain /home/hadoop/app/zookeeper-3.4.6/bin/../conf/zoo.cfg

root 2086 1861 0 20:32 pts/0 00:00:00 grep java

[root@weekend110 hsperfdata_root]# ll

total 32

-rw-------. 1 root root 32768 Oct 22 20:31 2063

[root@weekend110 hsperfdata_root]# rm 2063

rm: remove regular file `2063'? y

[root@weekend110 hsperfdata_root]# ll

total 0

[root@weekend110 hsperfdata_root]# jps

2100 Jps

[root@weekend110 shell]# cat echo.sh

#!/bin/bash