1. What are the file management commands on Linux, their common usage methods and related examples.
1. Directory management class commands:
mkdir: Create directories
Common parameters:
- p: Automatically create parent directory on demand
- v: Display the detailed process
- m MODE: Given permissions directly
[root@localhost ~]# mkdir -pv -m 600 /tmp/a/b mkdir: created directory '/tmp/a' mkdir: created directory '/tmp/a/b' [root@localhost ~]# ls -ld /tmp/a/b drw-------. 2 root root 6 May 7 21:14 /tmp/a/b
rmdir: Delete empty directories
Common parameters:
- p: After deleting a directory, if its parent directory is empty, delete it together
- v: Display the detailed process
[root@localhost ~]# rmdir -pv /tmp/a/b rmdir: removing directory, '/tmp/a/b' rmdir: removing directory, '/tmp/a' rmdir: removing directory, '/tmp' rmdir: failed to remove directory '/tmp': Device or resource busy
2. File management class commands:
cp: Copy files
Single source replication: CP [OPTION] [-T] SOURCE DEST
If DEST does not exist: create this file beforehand and copy the data flow from the source file to DEST
If DEST exists: if DEST is a non-directory file, overwrite the target file; if DEST is a directory file, create a file with the same name as the source file in the DEST directory and copy its data stream
[root@localhost ~]# mkdir /tmp/src /tmp/dst
[root@localhost ~]# touch /tmp/src/file{1,2,3}
[root@localhost ~]# ls /tmp/src/ /tmp/dst
/tmp/dst:
/tmp/src/:
file1 file2 file3
[root@localhost ~]# cp /tmp/src/file1 /tmp/dst/
[root@localhost ~]# ls /tmp/dst/
file1
[root@localhost ~]# cp /tmp/src/file2 /tmp/dst/file1
cp: overwrite '/tmp/dst/file1'? y
[root@localhost ~]# ls /tmp/dst/
file1
[root@localhost ~]# cp /tmp/src/file2 /tmp/dst/
[root@localhost ~]# ls /tmp/dst/
file1 file2Multi-source replication: cp [OPTION]... SOURCE... DIRECTORY
cp [OPTION]... -t DIRECTORY SOURCE...
If DEST does not exist: error
If DEST exists: if DEST is a non-directory file, error; if DEST is a directory file, copy each file to the target directory separately and keep its original name.
Note: Multi-source replication only supports DEST as directory file
[root@localhost ~]# cp /tmp/src/* /tmp/dst1/ cp: target '/tmp/dst1/' is not a directory [root@localhost ~]# cp /tmp/src/* /tmp/dst/file cp: target '/tmp/dst/file' is not a directory [root@localhost ~]# cp /tmp/src/* /tmp/dst/ cp: overwrite '/tmp/dst/file1'? y cp: overwrite '/tmp/dst/file2'? y [root@localhost ~]# ls /tmp/dst file1 file2 file3
Common parameters:
- i: Interactive, i.e. alerting users to confirm before coverage
Note: The root user defaults to use the alias command with the - i parameter, the ordinary user defaults to use the command itself, and the root user also wants to use the command itself to add "" before the command.
[root@localhost ~]# alias alias cp='cp -i'
- f: Mandatory overwriting of target files
[root@localhost ~]# echo "123" > /tmp/src/file1 [root@localhost ~]# cp -f /tmp/src/file1 /tmp/dst/file1 cp: overwrite '/tmp/dst/file1'? y [root@localhost ~]# \cp -f /tmp/src/file1 /tmp/dst/file1 [root@localhost ~]# cat /tmp/dst/file1 123
- r, -R: Recursive copy directory
- d: Copy the symbolic link file itself, not the source file it points to
[root@localhost ~]# ln -s /tmp/src/file1 /tmp/src/filelink [root@localhost ~]# ls -l /tmp/src/ total 4 -rw-r--r--. 1 root root 4 May 7 23:55 file1 -rw-r--r--. 1 root root 0 May 7 23:46 file2 -rw-r--r--. 1 root root 0 May 7 23:46 file3 lrwxrwxrwx. 1 root root 14 May 8 00:08 filelink -> /tmp/src/file1 [root@localhost ~]# cp -d /tmp/src/filelink /tmp/dst/ [root@localhost ~]# ls -l /tmp/dst/ total 4 -rw-r--r--. 1 root root 4 May 8 00:02 file1 -rw-r--r--. 1 root root 0 May 7 23:57 file2 -rw-r--r--. 1 root root 0 May 7 23:57 file3 lrwxrwxrwx. 1 root root 14 May 8 00:09 filelink -> /tmp/src/file1 [root@localhost ~]# cp /tmp/src/filelink /tmp/dst/filelink1 [root@localhost ~]# ls -l /tmp/dst/ total 8 -rw-r--r--. 1 root root 4 May 8 00:02 file1 -rw-r--r--. 1 root root 0 May 7 23:57 file2 -rw-r--r--. 1 root root 0 May 7 23:57 file3 lrwxrwxrwx. 1 root root 14 May 8 00:09 filelink -> /tmp/src/file1 -rw-r--r--. 1 root root 4 May 8 00:12 filelink1
- a:-dR --preserve=all, archive, for archiving
- preserv=mode: permissions
ownership: principal and subgroup
Timestamps: timestamps
Context: security label (selinux security context)
xattr: Extended attributes
Links: symbolic links
all: all of the above attributes
mv: Moving files or renaming
mv [OPTION]... [-T] SOURCE DEST
mv [OPTION]... SOURCE... DIRECTORY
mv [OPTION]... -t DIRECTORY SOURCE..
Common parameters:
- i: Interactive, i.e. alerting users to confirm before moving
- f: Forced movement
[root@localhost ~]# mv /tmp/dst/file1 /tmp/dst/file4 [root@localhost ~]# ls -l /tmp/dst/ total 8 -rw-r--r--. 1 root root 0 May 7 23:57 file2 -rw-r--r--. 1 root root 0 May 7 23:57 file3 -rw-r--r--. 1 root root 4 May 8 00:02 file4 lrwxrwxrwx. 1 root root 14 May 8 00:09 filelink -> /tmp/src/file1 -rw-r--r--. 1 root root 4 May 8 00:12 filelink1
rm: Delete files
rm [OPTION]... FILE...
Common parameters:
- i: Interactive, which reminds users to confirm before deleting
- f: Forced deletion
- r: Recursive deletion
[root@localhost ~]# rm -rf /tmp/dst/ [root@localhost ~]# ls /tmp/dst ls: cannot access /tmp/dst: No such file or directory
3. File View Class Command:
ls: Lists the contents in the specified directory
Common parameters:
- a: Display all files, including hidden files
[root@localhost ~]# ls -a / . bin dev home lib64 mnt proc run srv tmp var .. boot etc lib media opt root sbin sys usr
- A: Display all files except. and..
[root@localhost ~]# ls -A / bin dev home lib64 mnt proc run srv tmp var boot etc lib media opt root sbin sys usr
- l: Long format lists, which show detailed properties of files
- h: Convert file size units in a human-readable manner; the results may be inaccurate
[root@localhost ~]# ls -lh / total 32K lrwxrwxrwx. 1 root root 7 Aug 3 2016 bin -> usr/bin dr-xr-xr-x. 3 root root 4.0K Aug 2 2016 boot drwxr-xr-x. 19 root root 3.1K Aug 2 2016 dev drwxr-xr-x. 132 root root 8.0K Aug 2 2016 etc drwxr-xr-x. 4 root root 90 Aug 2 2016 home lrwxrwxrwx. 1 root root 7 Aug 3 2016 lib -> usr/lib lrwxrwxrwx. 1 root root 9 Aug 3 2016 lib64 -> usr/lib64 drwxr-xr-x. 3 root root 18 Aug 2 2016 media drwxr-xr-x. 3 root root 17 Aug 2 2016 mnt drwxr-xr-x. 3 root root 15 Aug 3 2016 opt dr-xr-xr-x. 505 root root 0 Aug 3 2016 proc dr-xr-x---. 14 root root 4.0K Aug 2 2016 root drwxr-xr-x. 35 root root 1.2K May 7 21:26 run lrwxrwxrwx. 1 root root 8 Aug 3 2016 sbin -> usr/sbin drwxr-xr-x. 2 root root 6 Mar 13 2014 srv dr-xr-xr-x. 13 root root 0 Aug 3 2016 sys drwxrwxrwt. 17 root root 4.0K May 7 21:54 tmp drwxr-xr-x. 13 root root 4.0K Aug 3 2016 usr drwxr-xr-x. 22 root root 4.0K Aug 3 2016 var
- d: View the directory itself rather than its internal file list
[root@localhost ~]# ls -ld /etc drwxr-xr-x. 132 root root 8192 Aug 2 2016 /etc
- r: Reverse Display
[root@localhost ~]# ls -r / var tmp srv run proc mnt lib64 home dev bin usr sys sbin root opt media lib etc boot
- R: Recursive display
Note: File types on Linux systems are:
- file, regular file
d: directory, directory file
b: block device, block device file, supports random access in "block" units
c: character device, character device file, supports linear access in character
major number: the main device number, which identifies the device type and then determines the driver to load
minor number: secondary device number, used to identify different devices in the same type
l: symbolic link, symbolic link file
p: pipe, named pipe
s: socket, socket file
File: View the file content type
[root@localhost ~]# file /sbin/ss /sbin/ss: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.32, BuildID[sha1]=0x14230a7d5743155147230c263cb721757a49db89, stripped
cat: Connect and display files
Common parameters:
- n: Number the text line displayed
[root@localhost ~]# cat -n /etc/fstab 1 2# 3# /etc/fstab 4# Created by anaconda on Tue Aug 2 21:31:19 2016 5# 6# Accessible filesystems, by reference, are maintained under '/dev/disk' 7# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info 8# 9/dev/mapper/rhel-root / xfs defaults 1 1 10UUID=ce40e87b-854d-42dc-ac50-e1309101c43d /boot xfs defaults 1 2 11/dev/mapper/rhel-swap swap swap defaults 0 0 12/dev/cdrom/media/cdromiso9660defaults0 0
- E: Display line terminator$
[root@localhost ~]# cat -E /etc/issue \S$ Kernel \r on an \m$ $
tac: Connect and display files, which is the reverse display of cat
Common parameters:
- n: Number the text line displayed
- E: Display line terminator$
head: View the first n lines of the file
Common parameters:
- n # (-#): Line before viewing the file
[root@localhost ~]# head -n 10 /etc/passwd root:x:0:0:root:/root:/bin/bash bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin adm:x:3:4:adm:/var/adm:/sbin/nologin lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin sync:x:5:0:sync:/sbin:/bin/sync shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown halt:x:7:0:halt:/sbin:/sbin/halt mail:x:8:12:mail:/var/spool/mail:/sbin/nologin operator:x:11:0:operator:/root:/sbin/nologin
tail: n lines after viewing the file
Common parameters:
- n #(-#): After viewing the file # line
[root@localhost ~]# tail -5 /etc/passwd gnome-initial-setup:x:993:991::/run/gnome-initial-setup/:/sbin/nologin postfix:x:89:89::/var/spool/postfix:/sbin/nologin sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin tcpdump:x:72:72::/:/sbin/nologin linuxprobe:x:1000:1000:linuxprobe:/home/linuxprobe:/bin/bash
- f: Do not quit after viewing the contents of the end of the file, follow the new line (usually used to view system log information)
[root@localhost ~]# tail -f /var/log/messages May 7 22:18:40 localhost dbus[1088]: [system] Activating via systemd: service name='net.reactivated.Fprint' unit='fprintd.service' May 7 22:18:40 localhost systemd: Starting Fingerprint Authentication Daemon... May 7 22:18:41 localhost dbus-daemon: dbus[1088]: [system] Successfully activated service 'net.reactivated.Fprint' May 7 22:18:41 localhost dbus[1088]: [system] Successfully activated service 'net.reactivated.Fprint' May 7 22:18:41 localhost systemd: Started Fingerprint Authentication Daemon. May 7 22:18:41 localhost fprintd: ** (fprintd:4822): WARNING **: fprint init failed with error -99 May 7 22:18:41 localhost systemd: fprintd.service: main process exited, code=exited, status=157/n/a May 7 22:18:41 localhost systemd: Unit fprintd.service entered failed state. May 7 22:20:01 localhost systemd: Starting Session 9 of user root. May 7 22:20:01 localhost systemd: Started Session 9 of user root.
more: View files separately, flip the screen to the end of the file and exit automatically
less: Screen-split view of files, support up and down page flipping, query operations, press q to exit
2. Return value of command execution status and command line expansion of bash's working characteristics and demonstration of their examples.
1. bash outputs the result of command execution through the return value of state:
Success: 0
Failure: Random numbers between 1 and 255, with different results depending on commands and their functions
After the command is executed, its state return value is saved in the special variable $? Of bash, which can be viewed through echo $?
[root@localhost ~]# ls /boot/ config-3.10.0-123.el7.x86_64 grub2 initramfs-0-rescue-49da9e087d6e4f9dab50f2af4a9a5921.img initramfs-3.10.0-123.el7.x86_64.img initramfs-3.10.0-123.el7.x86_64kdump.img initrd-plymouth.img symvers-3.10.0-123.el7.x86_64.gz System.map-3.10.0-123.el7.x86_64 vmlinuz-0-rescue-49da9e087d6e4f9dab50f2af4a9a5921 vmlinuz-3.10.0-123.el7.x86_64 [root@localhost ~]# echo $? 0 [root@localhost ~]# ls /boot/error ls: cannot access /boot/error: No such file or directory [root@localhost ~]# echo $? 2
2. What is involved in command line expansion
~ Automatically expand to the user's home directory, or the specified user's home directory
[root@localhost ~]# cp /etc/issue ~/ [root@localhost ~]# ls ~/ 2017-05-07 anaconda-ks.cfg Downloads Music Templates 22:50 Desktop initial-setup-ks.cfg Pictures Videos 22:50:00 Documents issue Public
{}: A comma-separated list of paths can be hosted and expanded into multiple paths
[root@localhost ~]# touch /tmp/file{1..10}
[root@localhost ~]# ls /tmp/file*
/tmp/file1 /tmp/file2 /tmp/file4 /tmp/file6 /tmp/file8
/tmp/file10 /tmp/file3 /tmp/file5 /tmp/file7 /tmp/file93. Use the command line expansion function to complete the following exercises:
(1) Create / tmp directories: a_c, a_d, b_c, b_d
[root@localhost ~]# mkdir -pv /tmp/{a,b}_{c,d}
mkdir: created directory '/tmp/a_c'
mkdir: created directory '/tmp/a_d'
mkdir: created directory '/tmp/b_c'
mkdir: created directory '/tmp/b_d'
[root@localhost ~]# tree -L 1 /tmp/
/tmp/
├── a_c
├── a_d
├── b_c
├── b_d(2) Create / tmp/mylinux directory:
mylinux/
├── bin
├── boot
│ └── grub
├── dev
├── etc
│ ├── rc.d
│ │ └── init.d
│ └── sysconfig
│ └── network-scripts
├── lib
│ └── modules
├── lib64
├── proc
├── sbin
├── sys
├── tmp
├── usr
│ └── local
│ ├── bin
│ └── sbin
└── var
├── lock
├── log
└── run
[root@localhost ~]# mkdir -pv /tmp/mylinux/{bin,boot/grub,dev,etc/{rc.d/init.d,sysconfig/network-
scripts},lib/modules,lib64,proc,sbin,sys,tmp,usr/local/{bin,sbin},var/{lock,log,run}}
mkdir: created directory '/tmp/mylinux'
mkdir: created directory '/tmp/mylinux/bin'
mkdir: created directory '/tmp/mylinux/boot'
mkdir: created directory '/tmp/mylinux/boot/grub'
mkdir: created directory '/tmp/mylinux/dev'
mkdir: created directory '/tmp/mylinux/etc'
mkdir: created directory '/tmp/mylinux/etc/rc.d'
mkdir: created directory '/tmp/mylinux/etc/rc.d/init.d'
mkdir: created directory '/tmp/mylinux/etc/sysconfig'
mkdir: created directory '/tmp/mylinux/etc/sysconfig/network-scripts'
mkdir: created directory '/tmp/mylinux/lib'
mkdir: created directory '/tmp/mylinux/lib/modules'
mkdir: created directory '/tmp/mylinux/lib64'
mkdir: created directory '/tmp/mylinux/proc'
mkdir: created directory '/tmp/mylinux/sbin'
mkdir: created directory '/tmp/mylinux/sys'
mkdir: created directory '/tmp/mylinux/tmp'
mkdir: created directory '/tmp/mylinux/usr'
mkdir: created directory '/tmp/mylinux/usr/local'
mkdir: created directory '/tmp/mylinux/usr/local/bin'
mkdir: created directory '/tmp/mylinux/usr/local/sbin'
mkdir: created directory '/tmp/mylinux/var'
mkdir: created directory '/tmp/mylinux/var/lock'
mkdir: created directory '/tmp/mylinux/var/log'
mkdir: created directory '/tmp/mylinux/var/run'
[root@localhost ~]# tree /tmp/mylinux/
/tmp/mylinux/
├── bin
├── boot
│ └── grub
├── dev
├── etc
│ ├── rc.d
│ │ └── init.d
│ └── sysconfig
│ └── network-scripts
├── lib
│ └── modules
├── lib64
├── proc
├── sbin
├── sys
├── tmp
├── usr
│ └── local
│ ├── bin
│ └── sbin
└── var
├── lock
├── log
└── run
24 directories, 0 files4. What are the metadata information of documents, what are their meanings and how to view them? How to modify the timestamp information of a file.
1. The data of files are divided into metadata and data. Metadata describes the characteristics of data itself, including file path, file size, data block information, file type, file permission, ownership group, security information, timestamp information (access time, modification time, change time) and so on.
2. Viewing metadata information of files
stat: Display file or file system status
[root@localhost ~]# echo 123 > /tmp/testfile [root@localhost ~]# stat /tmp/testfile File: '/tmp/testfile' Size: 4 Blocks: 8 IO Block: 4096 regular file Device: fd00h/64768dInode: 102531229 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Context: unconfined_u:object_r:user_tmp_t:s0 Access: 2017-05-08 01:10:05.142639974 +0800 Modify: 2017-05-08 01:10:05.142639974 +0800 Change: 2017-05-08 01:10:05.142639974 +0800 Birth: -
3. Modification of file timestamp information
touch: modify file timestamps or create files
Common parameters:
- c: Do not create a specified file path when it does not exist
- a: Modify access time only
[root@localhost ~]# touch -a -t 05101223 /tmp/testfile [root@localhost ~]# stat /tmp/testfile File: '/tmp/testfile' Size: 4 Blocks: 8 IO Block: 4096 regular file Device: fd00h/64768dInode: 102531229 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Context: unconfined_u:object_r:user_tmp_t:s0 Access: 2017-05-10 12:23:00.000000000 +0800 Modify: 2017-05-08 01:13:30.103620135 +0800 Change: 2017-05-08 01:14:37.774613584 +0800 Birth: -
- m: Modify only modify time
[root@localhost ~]# touch -m -t 05111122 /tmp/testfile [root@localhost ~]# stat /tmp/testfile File: '/tmp/testfile' Size: 4 Blocks: 8 IO Block: 4096 regular file Device: fd00h/64768dInode: 102531229 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Context: unconfined_u:object_r:user_tmp_t:s0 Access: 2017-05-10 12:23:00.000000000 +0800 Modify: 2017-05-11 11:22:00.000000000 +0800 Change: 2017-05-08 01:15:16.110609873 +0800 Birth: -
- t STAMP [[CC]YY]MMDDhhmm[.ss]: Modifying the timestamp
5. How to define an alias for a command and how to refer to the execution result of another command in a command?
1. Define and revoke aliases
alias NAME='COMMAND'
Note: Only valid for the current shell process
unalias NAME
[root@localhost ~]# alias lsver='cat /etc/redhat-release' [root@localhost ~]# lsver Red Hat Enterprise Linux Server release 7.0 (Maipo) [root@localhost ~]# alias alias cp='cp -i' alias egrep='egrep --color=auto' alias fgrep='fgrep --color=auto' alias grep='grep --color=auto' alias l.='ls -d .* --color=auto' alias ll='ls -l --color=auto' alias ls='ls --color=auto' alias lsver='cat /etc/redhat-release' alias mv='mv -i' alias rm='rm -i' alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde' [root@localhost ~]# unalias lsver [root@localhost ~]# alias alias cp='cp -i' alias egrep='egrep --color=auto' alias fgrep='fgrep --color=auto' alias grep='grep --color=auto' alias l.='ls -d .* --color=auto' alias ll='ls -l --color=auto' alias ls='ls --color=auto' alias mv='mv -i' alias rm='rm -i' alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde'
2. Execution results of referencing another command
$(COMMAND) or `COMMAND'`
[root@localhost ~]# touch /tmp/file$(date +%F) [root@localhost ~]# touch /tmp/file`date +%T` [root@localhost ~]# ls /tmp/file* /tmp/file01:31:33 /tmp/file2017-05