Unix is case-sensitive. Terminate file entry by typing Control-d on a line by itself. Hold down the Control key and type d. On your screen, you will see:. To make a duplicate copy of a file, use the command cp. For example, to create an exact copy of the file called firstfile, you would type:. This results in two files with different names, each containing the same information.
The cp command works by overwriting information. If you create a different file called thirdfile and then type the following command:. Unix does not have a command specifically for renaming files. Instead, the mv command is used both to change the name of a file and to move a file into a different directory.
To change the name of a file, use the following command format where thirdfile and file3 are sample file names :. This command results in the complete removal of thirdfile , but a new file called file3 contains the previous contents of thirdfile.
Like cp, the mv command also overwrites existing files. For example, if you have two files, fourthfile and secondfile, and you type the command. As a result, fourthfile is renamed secondfile , but in the process secondfile is deleted. You may remove more than one file at a time by specifying a list of files to be deleted. For example,. Type y or yes to remove a file; type n or no to leave it intact.
The directory that you create will be a subdirectory within your current directory. For details on how to navigate directories and display the files and directories they contain, see List Contents and Navigate Unix Directories. The mv and cp commands can be used to put files into a directory.
Assume that you want to place some files from your current directory into a newly created directory called project1. The command. There will now be two copies of chapter1 , one in the current directory and one in project1. The elif statement checks to make sure the argument provided is a file, and if so, it verbosely uses the second echo to print the cp command to be used and then executes it.
If the single argument is not a file, the third echo prints an error message to that effect. In my home directory, if I execute the backup command so defined on the file checkCounts. If I execute it once more, I see a new file checkCounts. As planned, I can go on editing checkCounts.
In my last article, I promised you that repetitive tasks can often be easily streamlined through the use of shell scripts, shell functions, and shell aliases. Thanks for the coment, Artur, good point! I had called this a number of other things along the way. Probably should change this too. I think you should also consider using 'cp -av'. This preserves things like timestamps, which I often use when looking for some file I made some time ago, and when it was made helps me find it.
Thanks for this writeup! I had no idea that 'cp' was capable of this. GUIs often keep me a bit removed from the terminal. Also, I find it easier to simply work with a graphical file manager. These examples among a few others I've collected since transitioning to Linux are great reasons to open up the terminal! I'm curious about Greg Pittman's contribution, re: timestamps. He seems to make a good point and if so I love that use of the braces!
If the setenv option is set in sudoers , the command to be run has the SETENV tag set or the command matched is ALL , the user may set variables that would overwise be forbidden. See sudoers 5 for more information. In the latter case the error string is printed to stderr. If the directory does not exist or if it is not really a directory, the entry is ignored and no error is printed. This should not happen under normal circumstances.
The most common reason for stat 2 to return permission denied is if you are running an automounter and one of the directories in your PATH is on a machine that is currently unreachable. There are two distinct ways to deal with environment variables. There is effectively a whitelist for environment variables. In all cases, environment variables with a value beginning with are removed as they could be interpreted as bash functions. The list of environment variables that sudo allows or denies is contained in the output of sudo -V when run as root.
Note that the dynamic linker on most operating systems will remove variables that can control dynamic linking from the environment of setuid executables, including sudo. These type of variables are removed from the environment before sudo even begins execution and, as such, it is not possible for sudo to preserve them. To prevent command spoofing, sudo checks. Note, however, that the actual PATH environment variable is not modified and is passed unchanged to the program that sudo executes.
On systems that allow non-root users to give away files via chown 2 , if the timestamp directory is located in a directory writable by anyone e. However, because sudo checks the ownership and mode of the directory and its contents, the only damage that can be done is to hide files by putting them in the timestamp dir.
This is unlikely to happen since once the timestamp dir is owned by root and inaccessible by any other user, the user placing files there would be unable to get them back out. Please note that sudo will normally only log the command it explicitly runs. The same is true for commands that offer shell escapes including most editors.
Because of this, care must be taken when giving users access to commands via sudo to verify that the command does not inadvertently give the user an effective root shell. Note that this runs the commands in a sub-shell to make the cd and file redirection work.
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