File wildcards, file creation, copying, and other operations in linux

1: bash feature status return value

Variable $ ?, It is used to save the status of successful command execution. 0 indicates successful, 1-indicates failed, take the command ls as an example:

Execution successful

[Root @ localhost ~] # Ls/usr/
Bin etc games include lib lib64 libexec local sbin share src tmp
[Root @ localhost ~] # Echo $?
0
Command input error

[Root @ localhost ~] # Lss/usr
-Bash: lss: command not found
[Root @ localhost ~] # Echo $?
127
Command parameter input error

[Root @ localhost ~] # Ls/usrrr
Ls: cannot access/usrrr: No such file or directory
[Root @ localhost ~] # Echo $?
2
Other error statuses, $? The result is not 0.

2: expand the command line

2.1: use the command line to expand and create the \ _ c, a \ _ d, B \ _ c, B \ _ d files under/tmp.

[Root @ localhost ~] # Mkdir-pv {a, B }_{ c, d}
Mkdir: created directory 'a _ C'
Mkdir: created directory 'a _ d'
Mkdir: created directory 'B _ C'
Mkdir: created directory 'B _ d'
[Root @ localhost ~] # Ls-d {a, B }_{ c, d}
A_c a_d B _c B _d
2.2: create the following file under/tmp.

Write the image description here

[Root @ localhost ~] # Mkdir-pv/tmp/mylinux/{bin, boot/grub, etc {/rc. d/init. d,/sysconfig/network-scripts}, dev, lib/modules, lib64, proc, sbin, sys, tmp, usr/local {/bin,/sbin }, var {/lock,/log,/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
'-- Run24 directories, 0 files

3: How to define a command alias? How can I reference the results of another command in one command?
You can use the reverse quote "or $ () to reference the execution results of other commands:

Use quotation marks

[Root @ localhost ~] # Dirname 'which touch'
/Bin
 
# Display the path of the touch Command
Use $ ()

[Root @ localhost ~] # Dirname $ (which touch)
/Bin

4: show all files and directories in the/var directory that start with the letter "l" and end with a lower-case letter and contain at least one digit (which can contain other characters) in the middle.

[Root @ localhost ~] # Ls-d/var/l * [[: digit:] * [[: lower:]
/Var/l13u/var/lfs3k
5: displays the files and directories starting with any number and ending with a non-number in the/etc directory.
1
2
[Root @ localhost ~] # Ls-d/etc/[[: digit:] * [^ [: digit:]
/Etc/222kkk/etc/333uuu

6: displays files and directories in the/etc directory that start with a non-letter and are followed by a letter and any other characters of any length.

[Root @ localhost ~] # Ls-d/etc/[^ [: alpha:] [[: alpha:] *
/Etc/1djj

7: create a file starting with tfile in/tmp, followed by the current time

[Root @ localhost ~] # Touch/tmp/tfile-'date + % F-% H-% M-% s'
[Root @ localhost ~] # Touch/tmp/tfile-'date + % F-% H-% M-% s'
[Root @ localhost ~] # Ls/tmp
Tfile-2016-08-25-08-14-35 tfile-2016-08-25-08-14-36

8: copy the files starting with "p" in the/etc directory and ending with non-numbers to the/tmp/mytest1 directory.

[Root @ localhost ~] # Mkdir/tmp/mytest1
[Root @ localhost ~] # Cp-r/etc/p * [^ [: digit:]/tmp/mytest1/
[Root @ localhost ~] # Ls/tmp/mytest1/
Pam. d passwd-pki plymouth Uth pm popt. d postfix ppp prelink. conf. d printcap profile. d protocols

9: Copy all directories and files ending with. d in the/etc directory to the/tmp/mytest2 directory.

[Root @ localhost ~] # Mkdir/tmp/mytest2
[Root @ localhost ~] # Cp-r/etc/*. d/tmp/mytest2
[Root @ localhost ~] # Ls/tmp/mytest2
Bash_completion.d dracut. conf. d makedev. d prelink. conf. d rc1.d rc5.d statetab. d yum. repos. d
Chkconfig. d init. d modprobe. d profile. d rc2.d rc6.d sudoers. d
Cron. d ld. so. conf. d pam. d rc. d rc3.d rsyslog. d sysctl. d
Depmod. d logrotate. d popt. d rc0.d rc4.d rwtab. d xinetd. d

10: Copy all files starting with l, n, or m and ending with. conf to the/tmp/mytest3 directory.

[Root @ localhost ~] # Mkdir/tmp/mytest3
[Root @ localhost ~] # Cp-r/etc/[lmn] *. conf/tmp/mytest3
[Root @ localhost ~] # Ls/tmp/mytest3
Ld. so. conf libaudit. conf libuser. conf logrotate. conf mke2fs. conf nsswitch. conf