Linux Common commands

Objective

Every time after reading the Linux command, the brain is always blank, good memory as bad pen, this time to write down, for later review. It's all basic, but it's practical.

First day Linux Command

1. Set the Start screen

Init 3 Switch to character interface

Init 5 switch to graphical interface

Cd/etc = VI Inittab Last ID represents startup item, 3 characters, 5 graphics, 0 shutdown, 6 restart. It should be understood that it is not possible to change to 0 or 6, otherwise the system will shut down after rebooting or starting.

All in all, there are 2 ways to shut down the machine, because 0 means to shut down.

Init 0, direct shutdown, will not notify other users, not very friendly

Shutdown–h now, notify other users to shut down, more friendly, qualified administrator.

2,ls command, view files, not much to say, usage, man a bit.

3,. Current directory,.. The upper directory,/represents the root directory. What does not add back to the working directory after the CD

4,pwd Show current directory

5,cat viewing the contents of a file

6,grep Find content Lookup files, content retrieval commands

7,find directory –name file name, finding files

8,RM file name, deleting files

RM–F file name, forced to delete files, file does not exist without error

RM–RF directory names, recursively delete directories and files within directories

9,CP File New file, copy

10,MV files, new files, same directory, renaming, different directories, moving

11,clear Clear Screen

12,ps View process information –a all processes,-u verbose,-x background process,-aux combination

13,top Viewing performance

14,whoami, who I am, not much.

15,who, see who logged into the system

16,TAR–CVF Xx.tar file 1 file 2 ... File packaging

TAR–XVF Xx.tar release the packaged files

Note: Tar is only packaged, not compressed

Gzip Xx.tar, compress file asked XX.tar.gz, the original tar file will be deleted

Gzip–d XX.tar.gz Extract Files

Linux compressed files in two steps, first tar packaging, in gzip compression

The next day Linux Command

1, new user useradd–d/home/xx xx = passwd xx

2, Switch User su-xx

3, let Linux look for executable files under the current path

CD (What does not write, back to the current host directory)

=>vi. Bash_profile

+ = Append to path:., indicating that the executable file can be found in the current directory

=>:wq, save exit

=>. . Bash_profile, as amended to take effect.

4,reboot restart

Third Day GCC

1,gcc–o Specify target file name example: Gcc–o destination file name source file name

2,gcc–e Precompiled file Example: Gcc–o target file name –E source file name

3, precompiled: Replace the included library file with the source file

4,gcc–c Compile source file (not linked) Example: gcc–c source file –o destination file

Gcc–s Generating assembly code example: Gcc–s source file-o destination file

5,linux files do not look for extensions, GCC distinguishes between file types according to the extension name

6,GCC can compile C + + files, but the link fails because the GCC default link C's library does not link C + + libraries

Combined with the above explanation, you can use the-l option to compile C + + files using GCC, which links C + + libraries with the-l command

Example: Gcc–o target file name –lstdc++ source file (CPP file)

7,NM File name View label

8, when the Make command is executed, the makefile file in the current directory is automatically searched

Makefile notation

->makefile default is based on dependency execution, no dependent statements do not execute

Specify statement designator to execute the specified statement, for example: Make clean

9, in order to strengthen GDB debugging, generate Corefile steps

Cd=> in. BASHRC finally add ulimit–c unlimited=>. . BASHRC, execute file, modify effective

10, using the core file debug program

The program run information is written to the core file, so we can look directly at the core file for error messages

Method: GdB Executable Core file

11, Direct Debugging program ※ Black Bold for command interpretation

Gdb-q executable file

Quit-> Exit

Run

Where-> Display Error location

List[m,n]-> Displays the context code for the error line, which displays the top and bottom lines of the error by default

print-> Monitoring Example: Print i

Continue-> continues to run, equivalent to jumping directly to the next breakpoint

Info break-> Viewing breakpoints

Delete breakpoint number, remove breakpoint

Set variable variable name = value Change variable value

Step-> Step in

Next-> Step over

Return [value]-> early termination of function execution

12,man tips: Man 2 XX View system calls

Man 3 XX View library functions

Man 5 XX View third-party libraries

Linux Common commands