下面的输出中，涉及到标准输出的，有十几行的那些，只列举了其中四五行
概念 #
- 标准输入，标准输出，标准错误
- 标准输出：打印到屏幕上的输出
╭─ ~ ly@vmmin 12:31:44
╰─❯ ls
content.zh index.html myfile
dufs.log install.sh shellTest
╭─ ~ ly@vmmin 12:32:21
╰─❯ echo $?
0
- 标准错误
╭─ ~ ly@vmmin 12:30:27
╰─❯ ls /notexist
ls: cannot access '/notexist': No such file or directory
╭─ ~ ly@vmmin 12:30:59
╰─❯ echo $?
2
标准输出和标准错误 #
部分重定向 #
标准错误重定向 2> #
find，文件系统
find /etc -type f
## 下面是附加知识，最后没用到
#新建一个用户，-m 让用户具有默认主目录，-d指定目录，-s指定用户登入后所使用的shell
sudo useradd -d /home/ly1 -s /bin/bash -m ly1
#设置密码
sudo passwd ly1
为了演示错误，先创建几个文件
root@vmmin:/home/ly# mkdir a && touch a/a1.txt a/a2.txt
root@vmmin:/home/ly# mkdir b && touch b/b1.txt b/b2.txt
#去除所在组和其他人的所有权限
root@vmmin:/home/ly# chmod 700 a
root@vmmin:/home/ly# chmod 700 b
╭─ ~ ly@vmmin 17:02:36
╰─❯ ls -l
total 80
drwx------ 2 root root 4096 Dec 23 16:13 a
-rw-r--r-- 1 ly ly 17006 Dec 23 16:04 abc.txt
drwx------ 2 root root 4096 Dec 23 16:13 b
drwxr-xr-x 3 ly ly 4096 Dec 18 17:33 content.zh
-rw-r--r-- 1 ly ly 90 Dec 20 11:20 dufs.log
-rw-r--r-- 1 ly ly 19786 Dec 17 23:54 index.html
-rw-r--r-- 1 ly ly 18369 Dec 19 15:01 install.sh
-rw-r--r-- 1 ly ly 0 Dec 20 22:27 myfile
drwxr-xr-x 3 ly ly 4096 Dec 23 10:34 shellTest
用root账号，在/home/ly下面创建了a，b文件夹，以及a1.txt，a2.txt，b1.txt，b2.txt
，a，b文件夹的权限均为700
使用find查找，会出现Permission错误
这里使用-not -path "/home/ly/.**"忽略点开头的文件
╭─ ~ ly@vmmin 17:02:38
╰─❯ find ~ -type f -not -path "/home/ly/.**"
find: ‘/home/ly/a’: Permission denied
/home/ly/dufs.log
find: ‘/home/ly/b’: Permission denied
/home/ly/index.html
/home/ly/abc.txt
/home/ly/shellTest/2myscript_cls.sh
/home/ly/shellTest/82myscript_cls.sh
/home/ly/shellTest/62myscript_cls.sh
/home/ly/shellTest/31myscript_cls.sh
/home/ly/shellTest/92myscript_cls.sh
忽略显示错误的信息
╭─ ~ ly@vmmin 17:05:37
╰─❯ find ~ -type f -not -path "/home/ly/.**" 2> /dev/null
/home/ly/dufs.log
/home/ly/index.html
/home/ly/abc.txt
/home/ly/shellTest/2myscript_cls.sh
/home/ly/shellTest/82myscript_cls.sh
/home/ly/shellTest/62myscript_cls.sh
/home/ly/shellTest/31myscript_cls.sh
/home/ly/shellTest/92myscript_cls.sh
/home/ly/shellTest/61myscript_cls.sh
/home/ly/shellTest/32myscript_cls.sh
/home/ly/shellTest/64myscript_cls.sh
/home/ly/shellTest/65myscript_cls.sh
/home/ly/shellTest/53myscript_cls.sh
/home/ly/shellTest/72myscript_cls.sh
/home/ly/shellTest/52myscript_cls.sh
/home/ly/shellTest/81myscript_cls.sh
╭─ ~ ly@vmmin 17:05:47
╰─❯ echo $?
1
echo $?结果为1说明其实出错了，但是没有显示。
>号用来重定向 /dev/null dev null
构成错误-标准错误的每一行将被发送到Dev null而不是屏幕
标准输出重定向1>或> #
╭─ ~ ly@vmmin 17:12:43
╰─❯ find ~ -type f -not -path "/home/ly/.**" > /dev/null
find: ‘/home/ly/a’: Permission denied
find: ‘/home/ly/b’: Permission denied
1> 和 > 是一样的结果，都是重定向标准输出
╭─ ~ ly@vmmin 17:12:43
╰─❯ find ~ -type f -not -path "/home/ly/.**" 1> /dev/null
find: ‘/home/ly/a’: Permission denied
find: ‘/home/ly/b’: Permission denied
重定向到文件 #
╭─ ~ ly@vmmin 17:15:07
╰─❯ find ~ -type f -not -path "/home/ly/.**" 1> file.txt
find: ‘/home/ly/a’: Permission denied
find: ‘/home/ly/b’: Permission denied
╭─ ~ ly@vmmin 17:16:35
╰─❯ cat file.txt
/home/ly/dufs.log
/home/ly/index.html
/home/ly/file.txt
/home/ly/abc.txt
/home/ly/shellTest/2myscript_cls.sh
/home/ly/shellTest/82myscript_cls.sh
/home/ly/shellTest/62myscript_cls.sh
/home/ly/shellTest/31myscript_cls.sh
/home/ly/shellTest/92myscript_cls.sh
/home/ly/shellTest/61myscript_cls.sh
/home/ly/shellTest/32myscript_cls.sh
/home/ly/shellTest/64myscript_cls.sh
/home/ly/shellTest/65myscript_cls.sh
/home/ly/shellTest/53myscript_cls.sh
同时重定向标准输出和标准错误 #
同时重定向到一个 #
在Shell中，标准错误写法为 2>, 标准输出为 1> 或者 >。如要要将标准输出和标准错误合二为一，都重定向到同一个文件，可以使用下面两种方式:
&> #
╭─ ~ ly@vmmin 17:22:07
╰─❯ find ~ -type f -not -path "/home/ly/.**" &> file.txt
╭─ ~ ly@vmmin 17:22:14
╰─❯ cat file.txt
find: ‘/home/ly/a’: Permission denied
/home/ly/dufs.log
find: ‘/home/ly/b’: Permission denied
/home/ly/index.html
/home/ly/file.txt
/home/ly/abc.txt
/home/ly/shellTest/2myscript_cls.sh
/home/ly/shellTest/82myscript_cls.sh
/home/ly/shellTest/62myscript_cls.sh
/home/ly/shellTest/31myscript_cls.sh
/home/ly/shellTest/92myscript_cls.sh
/home/ly/shellTest/61myscript_cls.sh
2>&1 #
╭─ ~ ly@vmmin 17:24:41
╰─❯ find ~ -type f -not -path "/home/ly/.**" > file.txt 2>&1
╭─ ~ ly@vmmin 17:24:57
╰─❯ cat file.txt
find: ‘/home/ly/a’: Permission denied
/home/ly/dufs.log
find: ‘/home/ly/b’: Permission denied
/home/ly/index.html
/home/ly/file.txt
/home/ly/abc.txt
/home/ly/shellTest/2myscript_cls.sh
/home/ly/shellTest/82myscript_cls.sh
/home/ly/shellTest/62myscript_cls.sh
/home/ly/shellTest/31myscript_cls.sh
/home/ly/shellTest/92myscript_cls.sh
一条语句分别重定向到多个 #
╭─ ~ ly@vmmin 17:30:48
╰─❯ find ~ -type f -not -path "/home/ly/.**" 1>find_results.txt 2>find_errors.txt
╭─ ~ ly@vmmin 17:31:06
╰─❯ cat find_results.txt
/home/ly/dufs.log
/home/ly/index.html
/home/ly/file.txt
/home/ly/abc.txt
/home/ly/shellTest/2myscript_cls.sh
/home/ly/shellTest/82myscript_cls.sh
/home/ly/shellTest/62myscript_cls.sh
/home/ly/shellTest/31myscript_cls.sh
/home/ly/shellTest/92myscript_cls.sh
/home/ly/shellTest/61myscript_cls.sh
/home/ly/shellTest/32myscript_cls.sh
/home/ly/shellTest/64myscript_cls.sh
╭─ ~ ly@vmmin 17:31:24
╰─❯ cat find_errors.txt
find: ‘/home/ly/a’: Permission denied
find: ‘/home/ly/b’: Permission denied
也可以使用find ~ -type f -not -path "/home/ly/.**" >find_results.txt 2>find_errors.txt
update脚本（之前的） #
╭─ ~ ly@vmmin 17:36:08
╰─❯ cat /usr/local/bin/update
#!/bin/bash
release_file=/etc/os-release
if grep -q "Arch" $release_file
then
sudo pacman -Syu
fi
if grep -q "Ubuntu" $release_file || grep -q "Debian" $release_file
then
sudo apt update
sudo apt dist-upgrade
fi
修改
╭─ ~/shellTest ly@vmmin 17:46:55
╰─❯ cat 11_1_1myscript_cls.sh
#!/bin/bash
release_file=/etc/os-release
logfile=/var/log/updater.log
errorlog=/var/log/updater_errors.log
if grep -q "Arch" $release_file
then
sudo pacman -Syu 1>>$logfile 2>>$errorlog
if [ $? -ne 0 ]
then
echo "An error occured,please check the $errorlog file."
fi
fi
if grep -q "Ubuntu" $release_file || grep -q "Debian" $release_file
then
sudo apt update 1>>$logfile 2>>$errorlog
if [ $? -ne 0 ]
then
echo "An error occured,please check the $errorlog file."
fi
sudo apt dist-upgrade -y 1>>$logfile 2>>$errorlog
if [ $? -ne 0 ]
then
echo "An error occured,please check the $errorlog file."
fi
fi
切换到root用户并执行
╭─ ~/shellTest ly@vmmin 17:50:25
╰─❯ su root -
Password:
root@vmmin:/home/ly/shellTest# ./11_1_1myscript_cls.sh
查看
#root用户下
root@vmmin:/home/ly/shellTest# cat /var/log/updater.log
Hit:1 https://mirrors.tuna.tsinghua.edu.cn/debian bookworm InRelease
Hit:2 https://mirrors.tuna.tsinghua.edu.cn/debian bookworm-updates InRelease
Hit:3 https://mirrors.tuna.tsinghua.edu.cn/debian bookworm-backports InRelease
Hit:4 https://mirrors.tuna.tsinghua.edu.cn/debian-security bookworm-security InRelease
Hit:5 https://security.debian.org/debian-security bookworm-security InRelease
Reading package lists...
Building dependency tree...
Reading state information...
All packages are up to date.
Reading package lists...
Building dependency tree...
Reading state information...
Calculating upgrade...
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
root@vmmin:/home/ly/shellTest# cat var/log/updater_errors.log
cat: var/log/updater_errors.log: No such file or directory
#这里没有出错，所以甚至连错误文件都没有
附加知识，监听文本文件
╭─ ~ ly@vmmin 18:00:17
╰─❯ sudo tail -f /var/log/updater.log
Hit:5 https://security.debian.org/debian-security bookworm-security InRelease
Reading package lists...
Building dependency tree...
Reading state information...
All packages are up to date.
Reading package lists...
Building dependency tree...
Reading state information...
Calculating upgrade...
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
标准输入 #
╭─ ~/shellTest 5s ly@vmmin 18:07:53
╰─❯ cat 11_2myscript_cls.sh
#!/bin/bash
echo "Please enter your name:"
read myname
echo "Your name is: $myname"
╭─ ~/shellTest 1m 6s ly@vmmin 18:07:42
╰─❯ ./11_2myscript_cls.sh
Please enter your name:
JayH
Your name is: JayH