[Shell script] Pipes

Giả sử bạn muốn xem  hiện tại trong hệ thống có những gói rpm nào được cài đặt và muốn sắp xếp chúng theo một thứ tự nhất định. Khi đó, dựa vào I/O redirection thì giải pháp có thể là sử dụng 2 dòng lệnh:

Bookmark các câu lệnh trong Linux

Đây là nơi tôi ghi nhớ các câu lệnh khi làm việc với LInux.
+fuser: to identify processes using file or socket.
---Usage---
When you try to umount some mount point, maybe receive an error alert like: Device is busy...So, you can identify what processes using mount point, and use kill to kill that process...
+df: disk free
---Usage---
To view the space and state of all partitions
+rpm: install/uninstall software with rpm package
---Usage---
Some useful and often using option:
-Try to uninstall a software when unknown the full name of that package.
use: rpm -qa | grep
ie:when you want to uninstall VMware
command: rpm -qa | grep VM
+ldd
---Usage---
syntax:
ldd [program]
This command will show what library is neccessary for this program.
ex:
[cuong@CentOS5 Ebooks and Documents]$ ldd /bin/bash
linux-gate.so.1 => (0x00e74000)
libtermcap.so.2 => /lib/libtermcap.so.2 (0x07471000)
libdl.so.2 => /lib/libdl.so.2 (0x0076d000)
libc.so.6 => /lib/libc.so.6 (0x005e8000)
/lib/ld-linux.so.2 (0x005c9000)
+fsck
---Usage---
Check error for filesystem
+ln
---Usage---
make a link between files
syntax:
ln filename newname
when make link with the path, ln called symbolic link or symlink.
syntax:
ln /path/to/old/file /path/to/new/file
+find
---Usage---
To find files
ex:
find /bin -name ls
How the command above works?!
that command will look up in /bin firectory and find any file that named ls, when found, it will display to screen
+wc
---Usage---
wc-word count-the command to display the whole file. It will display the line, words, bytes of file
ex:
[cuong@CentOS5 27-6]$ ls
text1.txt
[cuong@CentOS5 27-6]$ wc text1.txt
1 6 25 text1.txt

As you see, wc counts the line, words, and bytes of text1.txt: 1 line, 6 words, 25 bytes
+tail
---Usage---
Print the last 10 lines of file to standard output
ex:

[cuong@CentOS5 27-6]$ wc tex2.txt
15 13 30 tex2.txt
[cuong@CentOS5 27-6]$ tail tex2.txt
t
y
u
w
d
x
h
j
ky
+split: split file into smaller parts 
usage: this command will split a file into smaller parts tha you can specific some characteristics for each parts. Assume i have a file of 12GB, i want split that file into some parts that each part is 4GB to burn into DVD disk, so i could use this option for split command:
#split 4048M myfile  mypart

This command will devide myfile into some smaller files and each file is 4048M(~4gb) and the splitted files name are begin with mypart( mypartaa, mypartab...).