File system security
$ ls -l (l for long listing!)
This command will let you get lots of detail about the contents of your directory, similar to the example below.
For example, here is a directory's details:
drwxr-xr-x 8 imac staff 272 7 12 10:48 test
最左邊的這一串10個字符的解釋：
- This column is a 10 symbol string consistingof the symbols d,r,w,x,-,and,occasionally, s or S. 這串字符由d、r、w、x略号、- 以及s诬留、S構(gòu)成的十個字符組成。
- If it starts with d, then this indicates a directory.Otherwise, - will be the starting symbol of the string.如果這串字符以d開頭，則說明這是一個目錄晤碘，否則其他是以 - 開頭衍锚。
- The 9 remaining symbols indicate the permission, or access rights, and are taken as three groups of 3.
剩下的9個字符友题，分別表示了允許進入權(quán)限等信息，3個為一組分成3組數(shù)戴质。
1.The left group of 3 givs the file permission for the user that owns the file( or directory);最左邊的3個字符表示給文件的主人用戶對文件進行讀寫執(zhí)行的權(quán)限度宦。這里的ownner是imac。
2.The middle group gives the permissions for the group of people to whom the file(or directory) belongs; 中間的3個字符表示對擁有該文件的用戶授予的文件讀寫執(zhí)行的權(quán)限告匠。這里是staff戈抄。
3.The mostright group gives the permissions for all others. 最右邊的三個表示對其他用戶的權(quán)限支持。
Access rights on files.
r (or -), indicates read permission (or otherwise), that is, the presence or absence of permission to read and copy the file
w (or -), indicates write permission (or otherwise), that is, the permission (or otherwise) to change a file
x (or -), indicates execution permission (or otherwise), that is, the permission to execute a file, where appropriate
Changing access rights
Using chmod to change the access rights of the file testfile.
The options of chmod are as follows:
| Sybol符號 | Meaning意思 |
|---|---|
| u | user 用戶 |
| g | group 組 |
| o | other 其他 |
| a | all 所有人 |
| r | read 讀 |
| w | write（and delete）寫／刪 |
| x | execute（and access directory）執(zhí)行和進入目錄 |
| u | user 用戶 |
$ chmod go-rwx testfile
This will remove read write and execute permissions on the file testfile for the group and others.取消（收回）組內(nèi)和其他人的讀寫后专、執(zhí)行testfile文件的權(quán)限划鸽。
$ chmod a+rw testfile
This will give read and write permissions on the file testfile to all.給予所有人讀寫testfile的權(quán)限。
Processes and Jobs
A process is an executing program identified by a unique PID (process identifer).
$ ps
This command will help you to see information about your processes, like their associated PID and status.查看進程的狀態(tài)信息戚哎，PID裸诽、運行狀態(tài)等。
A process may be in the foreground, in the background, or be suspended. In general the shell does not return the UNIX prompt until the current process has finished executing.進程的狀態(tài)有三種：前臺型凳、后臺丈冬、被掛起。
把長進程放在后臺甘畅，可以讓UNIX prompt立刻返回結(jié)果埂蕊，同時其他任務還在繼續(xù)執(zhí)行。
Running background processes
To background a process, type an & at the end of command line.
For example, the command sleep waits a given number of seconds before continuing.
$ sleep 10
This will wait 10 seconds before returning the command prompt %. Until the command prompt is returned, you can do nothing except wait.讓進程睡眠十秒鐘疏唾，這段時間你什么操作都不能做蓄氧。
$ sleep 10 &
The & runs the job in the background and returns the prompt straight away, allowing you to do run other programs while waiting for that one to finish. &符號在后臺執(zhí)行sleep命令，在窗口會立刻提示荸实，你可以做其他操作匀们。
Backgrounding a current foreground process
At the prompt, type
$ sleep 1000
Then you can suspend the process runing in the foreground by typing ^Z, Then to put it in the background:
$ bg
這樣能夠讓在前臺執(zhí)行中的程序掛起。
Listing suspended and background processes
$ jobs
This can list processes are running,backgrounded or suspended with their job numbers.
把所有執(zhí)行中准给、后臺的泄朴、掛起的程序列出，并且有一個job number露氮。
$ fg $jobnumber
To restart(foreground) a suspended process.再次執(zhí)行掛起的進程祖灰。
Killing a process
To kill a job runing in the foreground, type ^C
$ sleep 100
^C
結(jié)束一個正在前臺執(zhí)行的進程。
To kill a suspended or background process :
$ kill $jobnumber
結(jié)束一個被掛起或在后臺的進程畔规。
To kill the processes by finding their process numbers(PIDS)
$ kill PID_number
Remember that using ps to show the process status to find out the PID.
通過PID來結(jié)束一個進程局扶。
