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![Command: chmod If you own the file, you can change it’s permissions with “chmod” Syntax: chmod [user/group/others/all]+[permission] [file(s)] Below we grant execute permission to all:](https://image.slidesharecdn.com/linux-commands-220730160147-cc4802a6/75/linux-commands-ppt-37-2048.jpg)
linux-commands.ppt
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- 2. Connecting to aUnix/Linux system Open up a terminal:
- 3. Connecting to aUnix/Linux system Open up a terminal: The “prompt” The current directory (“path”) The host
- 4. What exactly isa “shell”? After logging in, Linux/Unix starts another program called the shell The shell interprets commands the user types and manages their execution The shell communicates with the internal part of the operating system called the kernel The most popular shells are: tcsh, csh, korn, and bash The differences are most times subtle For this tutorial, we are using bash Shell commands are CASE SENSITIVE!
- 5. Help! Whenever you needhelp with a command type “man” and the command name
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- 9. Unix/Linux File System /home/john/portfolio/ /home/mary/ ThePath NOTE: Unix file names are CASE SENSITIVE!
- 10. Command: pwd To findyour current path use “pwd”
- 11. Command: cd To changeto a specific directory use “cd”
- 12. Command: cd “~”is the location of your home directory
- 13. Command: cd “..” isthe location of the directory below current one
- 14. Command: ls Tolist the files in the current directory use “ls”
- 15. Command: ls lshas many options -l long list (displays lots of info) -t sort by modification time -S sort by size -h list file sizes in human readable format -r reverse the order “man ls” for more options Options can be combined: “ls -ltr”
- 16. Command: ls -ltr List files by time in reverse order with long listing
- 17. General Syntax: * “*”can be used as a wildcard in unix/linux
- 18. Command: mkdir To createa new directory use “mkdir”
- 19. Command: rmdir To removeand empty directory use “rmdir”
- 20. Displaying a file Variousways to display a file in Unix cat less head tail
- 21. Command: cat Dumpsan entire file to standard output Good for displaying short, simple files
- 22. Command: less “less”displays a file, allowing forward/backward movement within it return scrolls forward one line, space one page y scrolls back one line, b one page use “/” to search for a string Press q to quit
- 23. Command: head “head” displaysthe top part of a file By default it shows the first 10 lines -n option allows you to change that “head -n50 file.txt” displays the first 50 lines of file.txt
- 24. Command: head Here’s anexample of using “head”:
- 25. Command: tail Same ashead, but shows the last lines
- 26. File Commands Copying afile: cp Move or rename a file: mv Remove a file: rm
- 27. Command: cp To copya file use “cp”
- 28. Command: mv Tomove a file to a different location use “mv”
- 29. Command: mv mv canalso be used to rename a file
- 30. Command: rm To removea file use “rm”
- 31. Command: rm To removea file “recursively”: rm –r Used to remove all files and directories Be very careful, deletions are permanent in Unix/Linux
- 32. File permissions Each filein Unix/Linux has an associated permission level This allows the user to prevent others from reading/writing/executing their files or directories Use “ls -l filename” to find the permission level of that file
- 33. Permission levels “r” means“read only” permission “w” means “write” permission “x” means “execute” permission In case of directory, “x” grants permission to list directory contents
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- 37. Command: chmod Ifyou own the file, you can change it’s permissions with “chmod” Syntax: chmod [user/group/others/all]+[permission] [file(s)] Below we grant execute permission to all:
- 38. Command: ps To viewthe processes that you’re running:
- 39. Command: top To viewthe CPU usage of all processes:
- 40. Command: kill To terminatea process use “kill”
- 41. Input/Output Redirection (“piping”) Programs can output to other programs Called “piping” “program_a | program_b” program_a’s output becomes program_b’s input “program_a > file.txt” program_a’s output is written to a file called “file.txt” “program_a < input.txt” program_a gets its input from a file called “input.txt”
- 42. A few examplesof piping
- 43. A few examplesof piping
- 44. Command: wc To countthe characters, words, and lines in a file use “wc” The first column in the output is lines, the second is words, and the last is characters
- 45. A few examplesof piping
- 46. Command: grep To searchfiles in a directory for a specific string use “grep”
- 47. Command: diff To compareto files for differences use “diff” Try: diff /dev/null hello.txt /dev/null is a special address -- it is always empty, and anything moved there is deleted