文件的输入与输出"/>
linux文件的输入与输出
目录
- 1、什么是输入输出
- 2、输出重定向
- 3 、输入重定向
1、什么是输入输出
1)字符设备
字符设备就是显示字符到屏幕上的设备文件
2)stdin
标准输入
编号为0
键盘 鼠标 打字机
3)stdout
标准正确输出
标号为1
4)stderr
标准错误输出
标号为2
打开shell输入的命令都会保存在打开shell的进程pid/fd/0里面，回车后通过cpu计算，正确输出保存到pid/fd/1里面，错误输出保存到pid/fd/2里面，他们共同显示到字符设备/dev/pts/x里
2、输出重定向
通俗的讲，重定向输出就是把输出的文件信息写入到一个文件中去，而不是将要输出的文件信息输出到控制台（显示屏）
1>
重定向正确输出
利用root用户在/etc目录下查询passwd文件：将查询的正确结果保存在file文件中，使用cat查询。
[root@foundation50 Desktop]# find /etc/ -name passwd > file
[root@foundation50 Desktop]# cat file
/etc/pam.d/passwd
/etc/passwd
2>
重定向错误输出
利用root用户在/etc目录下查询passwd文件：将查询的错误结果保存在file1文件中，使用cat查询，没有！。
利用普通用户在/etc目录下查询passwd文件：将查询的错误结果保存在file2文件中，使用cat查询。
[root@foundation50 Desktop]# su -- westos
[westos@foundation50 Desktop]$ find /etc -name passwd
find: ‘/etc/pki/rsyslog’: Permission denied
find: ‘/etc/lvm/archive’: Permission denied
find: ‘/etc/lvm/backup’: Permission denied
find: ‘/etc/lvm/cache’: Permission denied
find: ‘/etc/dhcp’: Permission denied
/etc/pam.d/passwd
/etc/passwd
find: ‘/etc/cups/ssl’: Permission denied
find: ‘/etc/grub.d’: Permission denied
find: ‘/etc/nftables’: Permission denied
find: ‘/etc/polkit-1/rules.d’: Permission denied
find: ‘/etc/polkit-1/localauthority’: Permission denied
find: ‘/etc/audit’: Permission denied
find: ‘/etc/libvirt’: Permission denied
find: ‘/etc/sssd’: Permission denied
find: ‘/etc/firewalld’: Permission denied
find: ‘/etc/sudoers.d’: Permission denied
[westos@foundation50 Desktop]$ find /etc -name passwd 2> file2 把错误输出存到file2
/etc/pam.d/passwd
/etc/passwd
[westos@foundation50 Desktop]$ cat file2
find: ‘/etc/pki/rsyslog’: Permission denied
find: ‘/etc/lvm/archive’: Permission denied
find: ‘/etc/lvm/backup’: Permission denied
find: ‘/etc/lvm/cache’: Permission denied
find: ‘/etc/dhcp’: Permission denied
find: ‘/etc/cups/ssl’: Permission denied
find: ‘/etc/grub.d’: Permission denied
find: ‘/etc/nftables’: Permission denied
find: ‘/etc/polkit-1/rules.d’: Permission denied
find: ‘/etc/polkit-1/localauthority’: Permission denied
find: ‘/etc/audit’: Permission denied
find: ‘/etc/libvirt’: Permission denied
find: ‘/etc/sssd’: Permission denied
find: ‘/etc/firewalld’: Permission denied
find: ‘/etc/sudoers.d’: Permission denied&>
重定向所有输出
在/etc目录下查询passwd文件：将查询的所有结果保存在file3文件中，使用cat查询
[westos@foundation50 Desktop]$ find /etc -name passwd &> file3
[westos@foundation50 Desktop]$ cat file3
find: ‘/etc/pki/rsyslog’: Permission denied
find: ‘/etc/lvm/archive’: Permission denied
find: ‘/etc/lvm/backup’: Permission denied
find: ‘/etc/lvm/cache’: Permission denied
find: ‘/etc/dhcp’: Permission denied
/etc/pam.d/passwd
/etc/passwd
find: ‘/etc/cups/ssl’: Permission denied
find: ‘/etc/grub.d’: Permission denied
find: ‘/etc/nftables’: Permission denied
find: ‘/etc/polkit-1/rules.d’: Permission denied
find: ‘/etc/polkit-1/localauthority’: Permission denied
find: ‘/etc/audit’: Permission denied
find: ‘/etc/libvirt’: Permission denied
find: ‘/etc/sssd’: Permission denied
find: ‘/etc/firewalld’: Permission denied
find: ‘/etc/sudoers.d’: Permission denied
利用重定向清空文件
[westos@foundation50 Desktop]$ > file3
[westos@foundation50 Desktop]$ cat file3
[westos@foundation50 Desktop]$
“>> 输出正确的追加，原内容不会被清空”
[westos@foundation50 Desktop]$ cat file3 原文件
/etc/pam.d/passwd
/etc/passwd
[westos@foundation50 Desktop]$ find /etc -name passwd >> file3
find: ‘/etc/pki/rsyslog’: Permission denied
find: ‘/etc/lvm/archive’: Permission denied
find: ‘/etc/lvm/backup’: Permission denied
find: ‘/etc/lvm/cache’: Permission denied
find: ‘/etc/dhcp’: Permission denied
find: ‘/etc/cups/ssl’: Permission denied
find: ‘/etc/grub.d’: Permission denied
find: ‘/etc/nftables’: Permission denied
find: ‘/etc/polkit-1/rules.d’: Permission denied
find: ‘/etc/polkit-1/localauthority’: Permission denied
find: ‘/etc/audit’: Permission denied
find: ‘/etc/libvirt’: Permission denied
find: ‘/etc/sssd’: Permission denied
find: ‘/etc/firewalld’: Permission denied
find: ‘/etc/sudoers.d’: Permission denied
[westos@foundation50 Desktop]$ cat file3
/etc/pam.d/passwd
/etc/passwd
/etc/pam.d/passwd
/etc/passwd
2>> 追加错误输出
[westos@foundation50 Desktop]$ cat file3 原文件
/etc/pam.d/passwd
/etc/passwd
[westos@foundation50 Desktop]$ find /etc -name passwd 2>> file3
/etc/pam.d/passwd
/etc/passwd
[westos@foundation50 Desktop]$ cat file3
/etc/pam.d/passwd
/etc/passwd
find: ‘/etc/pki/rsyslog’: Permission denied
find: ‘/etc/lvm/archive’: Permission denied
find: ‘/etc/lvm/backup’: Permission denied
find: ‘/etc/lvm/cache’: Permission denied
find: ‘/etc/dhcp’: Permission denied
find: ‘/etc/cups/ssl’: Permission denied
find: ‘/etc/grub.d’: Permission denied
find: ‘/etc/nftables’: Permission denied
find: ‘/etc/polkit-1/rules.d’: Permission denied
find: ‘/etc/polkit-1/localauthority’: Permission denied
find: ‘/etc/audit’: Permission denied
find: ‘/etc/libvirt’: Permission denied
find: ‘/etc/sssd’: Permission denied
find: ‘/etc/firewalld’: Permission denied
find: ‘/etc/sudoers.d’: Permission denied
&>>
追加所有输出到文件最后
[westos@foundation50 Desktop]$ cat file3
[westos@foundation50 Desktop]$ find /etc -name passwd &>> file3
[westos@foundation50 Desktop]$ cat file3
find: ‘/etc/pki/rsyslog’: Permission denied
find: ‘/etc/lvm/archive’: Permission denied
find: ‘/etc/lvm/backup’: Permission denied
find: ‘/etc/lvm/cache’: Permission denied
find: ‘/etc/dhcp’: Permission denied
/etc/pam.d/passwd
/etc/passwd
find: ‘/etc/cups/ssl’: Permission denied
find: ‘/etc/grub.d’: Permission denied
find: ‘/etc/nftables’: Permission denied
find: ‘/etc/polkit-1/rules.d’: Permission denied
find: ‘/etc/polkit-1/localauthority’: Permission denied
find: ‘/etc/audit’: Permission denied
find: ‘/etc/libvirt’: Permission denied
find: ‘/etc/sssd’: Permission denied
find: ‘/etc/firewalld’: Permission denied
find: ‘/etc/sudoers.d’: Permission denied
输出重定向会覆盖文件内容，追加重定向不会覆盖文件原来的内容
| 管道
"|"管道的作用是把前一条命令的 正确输出 变成后一条命令的输入
通过管道的输出将会变成输入，会被第二条命令处理
[westos@foundation50 Desktop]$ find /etc -name passwd | wc -l 正确的输出会被管道符通过，错误的不会通过
find: ‘/etc/pki/rsyslog’: Permission denied
find: ‘/etc/lvm/archive’: Permission denied
find: ‘/etc/lvm/backup’: Permission denied
find: ‘/etc/lvm/cache’: Permission denied
find: ‘/etc/dhcp’: Permission denied
find: ‘/etc/cups/ssl’: Permission denied
find: ‘/etc/grub.d’: Permission denied
find: ‘/etc/nftables’: Permission denied
find: ‘/etc/polkit-1/rules.d’: Permission denied
find: ‘/etc/polkit-1/localauthority’: Permission denied
find: ‘/etc/audit’: Permission denied
find: ‘/etc/libvirt’: Permission denied
find: ‘/etc/sssd’: Permission denied
find: ‘/etc/firewalld’: Permission denied
find: ‘/etc/sudoers.d’: Permission denied
2
如果让错误的输出也要被管道符通过，则需要把错误的输出追加到正确的输出里 2>&1
[westos@foundation50 Desktop]$ find /etc -name passwd 2>&1 | wc -l
17
若需要将输出内容保存一份，可以通过tee 复制两份，一份保存到文件里，一份通过管道让wc -l 来处理
[westos@foundation50 Desktop]$ find /etc -name passwd 2>&1 |tee file1 | wc -l
17
[westos@foundation50 Desktop]$ cat file1
find: ‘/etc/pki/rsyslog’: Permission denied
find: ‘/etc/lvm/archive’: Permission denied
find: ‘/etc/lvm/backup’: Permission denied
find: ‘/etc/lvm/cache’: Permission denied
find: ‘/etc/dhcp’: Permission denied
/etc/pam.d/passwd
/etc/passwd
find: ‘/etc/cups/ssl’: Permission denied
find: ‘/etc/grub.d’: Permission denied
find: ‘/etc/nftables’: Permission denied
find: ‘/etc/polkit-1/rules.d’: Permission denied
find: ‘/etc/polkit-1/localauthority’: Permission denied
find: ‘/etc/audit’: Permission denied
find: ‘/etc/libvirt’: Permission denied
find: ‘/etc/sssd’: Permission denied
find: ‘/etc/firewalld’: Permission denied
find: ‘/etc/sudoers.d’: Permission denied
3 、输入重定向
<
[root@foundation50 Desktop]# cat test
hello
HELLO
[root@foundation50 Desktop]# tr 'a-z' 'A-Z' < test 将shell的0（输入)定向到tr 程序的0里面，因为shell不具备转换大小写的功能
HELLO
HELLO
<<
多行输入重定向
vim westos.sh
date
passwd root << EOF << 表示多行输入 EOF 表示起始字符串
westos
westos
EOF 遇到EOF j结束
[root@foundation50 Desktop]# sh westos.sh 运行
Wed Aug 4 21:50:50 CST 2021
Changing password for user root.
New password: BAD PASSWORD: The password is shorter than 8 characters
Retype new password: passwd: all authentication tokens updated successfully.
练习：
4、[westos@foundation50 Desktop]$ find /etc -name passwd 2>&1 | tee /dev/pts/0 | wc -l #/dev/pts/o 放入字符设备，能显示出来的就叫字符设备
find: ‘/etc/pki/rsyslog’: Permission denied
find: ‘/etc/lvm/archive’: Permission denied
find: ‘/etc/lvm/backup’: Permission denied
find: ‘/etc/lvm/cache’: Permission denied
find: ‘/etc/dhcp’: Permission denied
/etc/pam.d/passwd
/etc/passwd
find: ‘/etc/cups/ssl’: Permission denied
find: ‘/etc/grub.d’: Permission denied
find: ‘/etc/nftables’: Permission denied
find: ‘/etc/polkit-1/rules.d’: Permission denied
find: ‘/etc/polkit-1/localauthority’: Permission denied
find: ‘/etc/audit’: Permission denied
find: ‘/etc/libvirt’: Permission denied
find: ‘/etc/sssd’: Permission denied
find: ‘/etc/firewalld’: Permission denied
find: ‘/etc/sudoers.d’: Permission denied
17
5、[westos@foundation50 Desktop]$ tr 'a-z' 'A-Z' < /etc/passwd | cat -n1 ROOT:X:0:0:ROOT:/ROOT:/BIN/BASH2 BIN:X:1:1:BIN:/BIN:/SBIN/NOLOGIN3 DAEMON:X:2:2:DAEMON:/SBIN:/SBIN/NOLOGIN4 ADM:X:3:4:ADM:/VAR/ADM:/SBIN/NOLOGIN5 LP:X:4:7:LP:/VAR/SPOOL/LPD:/SBIN/NOLOGIN6 SYNC:X:5:0:SYNC:/SBIN:/BIN/SYNC7 SHUTDOWN:X:6:0:SHUTDOWN:/SBIN:/SBIN/SHUTDOWN8 HALT:X:7:0:HALT:/SBIN:/SBIN/HALT9 MAIL:X:8:12:MAIL:/VAR/SPOOL/MAIL:/SBIN/NOLOGIN10 OPERATOR:X:11:0:OPERATOR:/ROOT:/SBIN/NOLOGIN11 GAMES:X:12:100:GAMES:/USR/GAMES:/SBIN/NOLOGIN12 FTP:X:14:50:FTP USER:/VAR/FTP:/SBIN/NOLOGIN13 NOBODY:X:65534:65534:KERNEL OVERFLOW USER:/:/SBIN/NOLOGIN14 DBUS:X:81:81:SYSTEM MESSAGE BUS:/:/SBIN/NOLOGIN15 SYSTEMD-COREDUMP:X:999:997:SYSTEMD CORE DUMPER:/:/SBIN/NOLOGIN16 SYSTEMD-RESOLVE:X:193:193:SYSTEMD RESOLVER:/:/SBIN/NOLOGIN17 TSS:X:59:59:ACCOUNT USED BY THE TROUSERS PACKAGE TO SANDBOX THE TCSD DAEMON:/DEV/NULL:/SBIN/NOLOGIN18 POLKITD:X:998:996:USER FOR POLKITD:/:/SBIN/NOLOGIN19 GEOCLUE:X:997:995:USER FOR GEOCLUE:/VAR/LIB/GEOCLUE:/SBIN/NOLOGIN20 RTKIT:X:172:172:REALTIMEKIT:/PROC:/SBIN/NOLOGIN21 PIPEWIRE:X:996:994:PIPEWIRE SYSTEM DAEMON:/VAR/RUN/PIPEWIRE:/SBIN/NOLOGIN22 PULSE:X:171:171:PULSEAUDIO SYSTEM DAEMON:/VAR/RUN/PULSE:/SBIN/NOLOGIN23 LIBSTORAGEMGMT:X:995:991:DAEMON ACCOUNT FOR LIBSTORAGEMGMT:/VAR/RUN/LSM:/SBIN/NOLOGIN24 QEMU:X:107:107:QEMU USER:/:/SBIN/NOLOGIN25 USBMUXD:X:113:113:USBMUXD USER:/:/SBIN/NOLOGIN26 UNBOUND:X:994:989:UNBOUND DNS RESOLVER:/ETC/UNBOUND:/SBIN/NOLOGIN27 RPC:X:32:32:RPCBIND DAEMON:/VAR/LIB/RPCBIND:/SBIN/NOLOGIN28 GLUSTER:X:993:988:GLUSTERFS DAEMONS:/RUN/GLUSTER:/SBIN/NOLOGIN29 CHRONY:X:992:987::/VAR/LIB/CHRONY:/SBIN/NOLOGIN30 SETROUBLESHOOT:X:991:985::/VAR/LIB/SETROUBLESHOOT:/SBIN/NOLOGIN31 SASLAUTH:X:990:76:SASLAUTHD USER:/RUN/SASLAUTHD:/SBIN/NOLOGIN32 DNSMASQ:X:984:984:DNSMASQ DHCP AND DNS SERVER:/VAR/LIB/DNSMASQ:/SBIN/NOLOGIN33 RADVD:X:75:75:RADVD USER:/:/SBIN/NOLOGIN34 CLEVIS:X:983:982:CLEVIS DECRYPTION FRAMEWORK UNPRIVILEGED USER:/VAR/CACHE/CLEVIS:/SBIN/NOLOGIN35 COCKPIT-WS:X:982:980:USER FOR COCKPIT WEB SERVICE:/NONEXISTING:/SBIN/NOLOGIN36 COCKPIT-WSINSTANCE:X:981:979:USER FOR COCKPIT-WS INSTANCES:/NONEXISTING:/SBIN/NOLOGIN37 SSSD:X:980:978:USER FOR SSSD:/:/SBIN/NOLOGIN38 FLATPAK:X:979:977:USER FOR FLATPAK SYSTEM HELPER:/:/SBIN/NOLOGIN39 COLORD:X:978:976:USER FOR COLORD:/VAR/LIB/COLORD:/SBIN/NOLOGIN40 GDM:X:42:42::/VAR/LIB/GDM:/SBIN/NOLOGIN41 RPCUSER:X:29:29:RPC SERVICE USER:/VAR/LIB/NFS:/SBIN/NOLOGIN42 GNOME-INITIAL-SETUP:X:977:975::/RUN/GNOME-INITIAL-SETUP/:/SBIN/NOLOGIN43 SSHD:X:74:74:PRIVILEGE-SEPARATED SSH:/VAR/EMPTY/SSHD:/SBIN/NOLOGIN44 AVAHI:X:70:70:AVAHI MDNS/DNS-SD STACK:/VAR/RUN/AVAHI-DAEMON:/SBIN/NOLOGIN45 RNGD:X:976:974:RANDOM NUMBER GENERATOR DAEMON:/VAR/LIB/RNGD:/SBIN/NOLOGIN46 TCPDUMP:X:72:72::/:/SBIN/NOLOGIN47 WESTOS:X:1000:1000::/HOME/WESTOS:/BIN/BASH48 APACHE:X:48:48:APACHE:/USR/SHARE/HTTPD:/SBIN/NOLOGIN
7、cat > westos.file << EOF
hello linux
hello westos
hello linux
westos linux is very nice
EOF
1、[westos@foundation50 Desktop]$ find /etc -name passwd 2> /dev/null
/etc/pam.d/passwd
/etc/passwd
内容补充
若让文件内容倒则显示 使用tac 命令
[root@foundation50 Desktop]# cat test
1
2
3
4
[root@foundation50 Desktop]# tac test
4
3
2
1
更多推荐
linux文件的输入与输出
发布评论