Shell中的test命令学习笔记2

Shell中的test命令(2)

文件比较
 

-d  file                    #检查file是否存在并是一个目录

-e  file                    #检查file是否存在

-f  file                    #检查file是否存在并是一个文件

-r  file                    #检查file是否存在并可读

-s  file                    #检查file是否存在并非空

-w  file                    #检查file是否存在并可写

-x  file                    #检查file是否存在并可执行

-O  file                    #检查file是否存在并且属当前用户所有

-G  file                    #检查file是否存在并且默认组与当前用户相同

file1 -nt file2             #检查file1是否比file2新   -nt  new

file1 -ot file2             #检查file1是否比file2旧   -ot  old 

 

#这些条件使你能在shell脚本中检查文件系统中的文件

并且经常用在要访问文件的脚本中，被广泛来使用

 

-d  file         #检查file是否存在并是一个目录

 

[root@localhost test]# cat 07.sh

#!/bin/bash

if [ -d $HOME ]         #判断是否存在用户的家目录

then
         echo "Your HOME directory exits"
         cd $HOME
         ls -a
else
         echo "There is a problem with your HOME directory"
fi

[root@localhost test]# sh 07.sh

Your HOME directory exits

.                .bashrc  Documents            Music          .viminfo

..               .cache   Downloads           Pictures   .xauthY2r7hE

anaconda-ks.cfg  .config  .esd_auth                  Public

.bash_history  .cshrc   .ICEauthority                  .tcshrc

.bash_logout  .dbus        initial-setup-ks.cfg      Templates

.bash_profile  Desktop  .local            Videos

 

$HOME ：也是个环境变量，系统已经提前给一些变量赋予了值，

$HOME获取当前用户的家目录(环境变量一般是大写的)

$USER：是获取当前系统登陆的用户

[root@localhost ~]# echo $HOME

/root

 

-e  file                     #检查file是否存在

#!/bin/bash

if [ -e $HOME ]

then

        echo "OK on the directory. now to check the file"

        if [ -e $HOME/testing ]

        then

                echo "Appending date to existing file"

                date >> $HOME/testing   

#将date命令的结果追加该文件中，不是覆盖

        else

                echo "Creating new file"

                date > $HOME/testing  

#输出重定向创建文件，且将date的内容放到新建的文件里面

        fi     

else

        echo "Sorry, you do not have a HOME directory"

fi

[root@localhost test]# sh 08.sh

OK on the directory. now to check the file

Creating new file

[root@localhost test]# cd

[root@localhost ~]# ls

anaconda-ks.cfg  Documents  initial-setup-ks.cfg  Pictures  Templates  Videos

Desktop          Downloads  Music                 Public    testing

[root@localhost ~]# cat testing

Wed Feb 12 23:04:26 CST 2020

 

第二次再执行这个文件时，就是追加了

[root@localhost ~]# cd -

/mnt/test

[root@localhost test]# sh 08.sh

OK on the directory. now to check the file

Appending date to existing file

[root@localhost test]# cd -

/root

[root@localhost ~]# cat testing

Wed Feb 12 23:04:26 CST 2020

Wed Feb 12 23:08:19 CST 2020

[root@localhost ~]#

 

-f  file                      #检查file是否存在并是一个文件

[root@localhost test]# cat 09.sh

#!/bin/bash

if [ -e $HOME ]
then
         echo "The object exists. is it a file ?"
         if [ -f $HOME ]
         then
                  echo "Yes. it is not a file!"
         else
                  echo "No. it is not a file!"
                  if [ -f $HOME/.bash_history ]
                  then
                          echo "But this is a file"
                  fi
         fi
else
         echo "Sorry. the object does not exist"
fi

[root@localhost test]# sh 09.sh

The object exists. is it a file ?

No. it is not a file!

But this is a file

[root@localhost ~]# ls -a

.                .bashrc  Documents             Music      Videos

..               .cache   Downloads             Pictures   .viminfo

anaconda-ks.cfg  .config  .esd_auth             Public     .xauthY2r7hE

.bash_history    .cshrc   .ICEauthority         .tcshrc

 

-r  file                      #检查file是否存在并可读

[root@localhost test]# cat 10.sh

#!/bin/bash

pwdfile=/etc/shadow

if [ -f $pwdfile ]

then
         if [ -r $pwdfile ]
         then
                  tail $pwdfile
         else
                  echo "Sorry. I am unable to read the $pwdfile file"
         fi
else
         echo "Sorry. the file $pwdfile dose not exist"
fi

[root@localhost test]# sh 10.sh

pulse:!!:18290::::::

gdm:!!:18290::::::

gnome-initial-setup:!!:18290::::::

avahi:!!:18290::::::

postfix:!!:18290::::::

ntp:!!:18290::::::

sshd:!!:18290::::::

tcpdump:!!:18290::::::

 

 

-s  file                      #检查file是否存在并非空

[root@localhost test]# cat 11.sh

#!/bin/bash

file=test

touch $file

if [ -s $file ]

then
         echo "The $file file exits and has data in it"
else
         echo "The $file  exists and is empty"
fi

[root@localhost test]# sh 11.sh

The test  exists and is empty

[root@localhost test]# ls

01.sh  03.sh  05.sh  07.sh  09.sh  11.sh

02.sh  04.sh  06.sh  08.sh  10.sh  test

[root@localhost test]# date

Thu Feb 13 09:02:58 CST 2020

[root@localhost test]# date > test

[root@localhost test]# vim test

[root@localhost test]#

[root@localhost test]# cat test

Thu Feb 13 09:03:08 CST 2020

[root@localhost test]# sh 11.sh

The test file exits and has data in it

 

-w  file                    #检查file是否存在并可写

脚本功能 : 测试是否可写，此脚本要在普通用户的权限测试

[root@localhost test]# cp 12.sh /home/student/     

#我们要使用student用户执行该脚本，将脚本拷到student的家目录下

[root@localhost test]# cd /home/student/

[root@localhost student]# ls

12.sh

[root@localhost student]# ll

total 4

-rw-r--r-- 1 root root 427 Feb 13 09:15 12.sh     

#我们可以看到其他普通用户的权限是r--

[root@localhost test]# cat 12.sh

#!/bin/bash

#测试是否可写

 

logfile=testroot

touch $logfile

chmod u-w $logfile

now=`date +%Y%m%d-%H%M`

 

if [ -w $logfile ]

then

         echo "The program ran at: $now" > logfile

         echo "The first attempt succeeded"

else

         echo "The first attempt failed"

 

chmod u+w $logfile

fi

if [ -w $logfile ]

then

         echo "The program ran at: $now" > logfile

        echo "The first attempt succeeded"

else

        echo "The first attempt failed"

fi

[root@localhost test]#

 

 

[root@localhost student]# chmod +x 12.sh

[root@localhost student]# ll 12.sh

-rwxr-xr-x 1 root root 427 Feb 13 09:15 12.sh

[root@localhost student]# su student

[student@localhost ~]$ ls

12.sh

[student@localhost ~]$ sh 12.sh

The first attempt failed

The first attempt succeeded

[student@localhost ~]$ ls

12.sh  logfile  testroot

脚本解读:

第一次判断时，testroot文件是不可写的，所以返回尝试失败，

紧接着给文件添加了写权限，再次执行上面的语句即可成功，

将当前时间重定向到logfile文件

 

-x  file             #检查file是否存在并可执行

 

[root@localhost test]# cat 13.sh

#!/bin/bash

if [ -x 10.sh ]

then

         echo "You can run the script"

         ./10.sh

else

         echo "Sorry. you are unable to execute the script"

fi

[root@localhost test]# ll 10.sh

-rw-r--r-- 1 root root 218 Feb 16 09:53 10.sh

[root@localhost test]# sh 13.sh

Sorry. you are unable to execute the script

 

-O  file                    #检查file是否存在并且属当前用户所有

 

 

[root@localhost test]# cat 14.sh

#!/bin/bash

if [ -O /etc/passwd  ]

then

         echo "You are the owner of the /etc/passwd file"

else

         echo "Sorry. you are not the owner of the /etc/passwd file"

fi

[root@localhost test]# ll /etc/passwd

-rw-r--r-- 1 root root 2235 Feb 12 15:45 /etc/passwd     

 

#我们可以看到这个文件的所属者是root

[root@localhost test]# sh 14.sh

You are the owner of the /etc/passwd file

[root@localhost test]#

 

 

-G  file                    #检查file是否存在并且默认组与当前用户相同

[root@localhost test]# cat 15.sh

#!/bin/bash

if [ -G $HOME/testing ]

then

         echo "You are in the same group as the file"

else 

         echo "The file is not owned by your group"

fi

[root@localhost test]# ll $HOME/testing

-rw-r--r-- 1 root root 58 Feb 12 23:08 /root/testing

[root@localhost test]# sh 15.sh

You are in the same group as the file

 

file1 -nt file2   #检查file1是否比file2新   -nt  new

 

file1 -ot file2    #检查file1是否比file2旧   -ot  old

 

[root@localhost test]# cat 16.sh

#!/bin/bash

if [ 01.sh -nt 02.sh ]

then

         echo "The 1.sh file is newer than 2.sh"

else

         echo "The 2.sh file is newer than 1.sh"

fi

 

if [ 03.sh -ot 04.sh ]

then

         echo "The 3.sh file is older than the 4.sh file"

fi

[root@localhost test]# sh 16.sh

The 2.sh file is newer than 1.sh

The 3.sh file is older than the 4.sh file