However, it also has many options for determining what processes to display, as well as the amount of information about each. For example, to view detailed information about all running processes, in a BSD system, you would use ps with the following arguments:. For more about ps refer to the ps man page on your system. Also see About the output fields of the ps command in Unix. For more, see Determine your current working directory in Unix. This command will remove destroy a file. You should enter this command with the -i option, so that you'll be asked to confirm each file deletion.
To remove a file named junk , enter:. Note: Using rm will remove a file permanently, so be sure you really want to delete a file before you use rm. To remove a non-empty subdirectory, rm accepts the -r option. On most systems this will prompt you to confirm the removal of each file.
This behavior can be prevented by adding the -f option. To remove an entire subdirectory named oldstuff and all of its contents, enter:. Note: Using this command will cause rm to descend into each subdirectory within the specified subdirectory and remove all files without prompting you. Use this command with caution, as it is very easy to accidently delete important files. As a precaution, use the ls command to list the files within the subdirectory you wish to remove. To browse through a subdirectory named oldstuff , enter:.
This command will remove a subdirectory. To remove a subdirectory named oldstuff , enter:. Note: The directory you specify for removal must be empty. To clean it out, switch to the directory and use the ls and rm commands to inspect and delete files. This command displays or changes various settings and options associated with your Unix session.
If the output scrolls off your screen, combine set with less :. The syntax used for changing settings is different for the various kinds of Unix shells; see the man entries for set and the references listed at the end of this document for more information.
This command starts the vi text editor. To edit a file named myfile in the current directory, enter:. The vi editor works fairly differently from other text editors. If you have not used it before, you should probably look at a tutorial, such as Use the vi text editor. The very least you need to know to start using vi is that in order to enter text, you need to switch the program from command mode to insert mode by pressing i.
To navigate around the document with the cursor keys, you must switch back to command mode by pressing Esc. To execute any of the following commands, you must switch from command mode to ex mode by pressing : the colon key : Enter w to save; wq to save and quit; q! The w and who commands are similar programs that list all users logged into the computer. If you use w , you also get a list of what they are doing. If you use who , you also get the IP numbers or computer names of the terminals they are using.
This is document afsk in the Knowledge Base. Last modified on Skip to: content search login. Knowledge Base Toggle local menu Menus About the team. Knowledge Base Search.
Log in. Options Help Chat with a consultant. Include archived documents. Introduction to Unix commands. The first example uses 3dcalc to convert a volume of r-value correlation values via the inverse hyperbolic tangent function a. The first set of quotes around [2] hide the [] characters from the shell passing them on to 3dcalc. Then the 3dcalc program knows to read in only volume 2, ignoring volumes 0, 1 and anything after 2.
The quotes around atanh a are to hide the characters, again so that 3dcalc sees that entire expression. Enclosing text in double quotes tells the shell not to interpret some of the enclosed special characters, but not as many as with single quotes. These examples just demonstrate use of variables within double quotes.
Back quotes are very different from single or double quotes. While single and double quotes are commonly used for hiding special characters from the shell, back quotes are used for command expansion. When putting back quotes around some text, the shell replaces the quoted text with the output of running the enclosed command. Examples will make it more clear.
The first example runs the command which afni , and puts the result back into the echo command. The second example line count -digits 2 1 6 simply shows the output from the AFNI count program, zero-padded 2 digit numbers from 1 to 6. The third line captures that output into a variable. Going off on a small tangent, that output is stored as a single value because of the double quotes.
The fourth line displays that output in the terminal window. The final echo line shows the same output as the previous echo line, except that now it shows that there are indeed 6 runs. The ctrl-c while holding the control key down, press c keystroke is used to terminate the foreground process in the current shell by sending it a SIGINT signal.
It is similar to ctrl-z, but rather than suspending a process, ctrl-c terminates it. This might be useful when running a shell script that would take a while to complete. Maybe you decide to make a change, or error messages start coming out.
If that script is running in the foreground, entering ctrl-c should terminate it. The ctrl-z while holding the control key down, press z keystroke is used to suspend the foreground process in the current shell. The process still exists, but will not run while in the suspended state.
This keystroke is often followed by bg background: a built-in shell command , to put the newly suspended process in the background. Alternatively, it could be followed by fg foreground: a build-in shell command , to put the suspended process back in the foreground, as it was in the first place.
Basic Unix : shell variables. Error messages. Enter search terms or a module, class or function name. Navigation index next previous unix tutorial 0. See also for geting help from the shell, use man , e. See also man tcsh. Note It is a good idea to follow a cd command with ls to list the contents of the new directory.
See also: bg See also man tcsh. Examples: jobs - probably shows nothing. See also man tcsh the example from: ctrl-z. Note A single set command can be used to set many variables, but such a use is not recommended. This is because Bash Shell Terminal is silent type. It will only show a message when something goes wrong or when an error has occurred. Executing the command. Currently, we are executing the command as a standard user. Hence we get the above error. To overcome the error use command.
Sudo program allows regular users to run programs with the security privileges of the superuser or root. Sudo command will ask for password authentication. Though, you do not need to know the root password. You can supply your own password. After authentication, the system will invoke the requested command.
Sudo maintains a log of each command run. System administrators can trackback the person responsible for undesirable changes in the system. NOTE : By default, the password you entered for sudo is retained for 15 minutes per terminal. This eliminates the need of entering the password time and again.
Enough with File manipulations! Use the below-given format:. Man stands for manual which is a reference book of a Linux operating system.
It is similar to HELP file found in popular software. For an example, if we type man man and hit enter; terminal would give us information on man command.
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