CSC 357 UNIX Basics

CSC 357 UNIX Basics

This handout has some bare-essential UNIX commands for dealing with files and directories. Chapter 1 of the Stevens book also has some introductory discussion of user-level UNIX commands. And there are links to additional UNIX resources in the 357 documentation directory.

Command	Description
`cp` source_file target_file `cp` source_file ... target_directory `cp ^_rp` source_directory target_directory	Copy files or directories. The first form copies the single source_file to the target_file. If the target exists, it is overwritten. If the target does not exist, it is created. The second form of `cp` copies one or more source_files into the target_directory. The target must exist. The third form recursively copies an entire source_directory hierarchy to the target_directory. If the target exists, the source is copied into it. If the target does not exist, it is created.
`mv` source target	Move the source file or directory to the target file or directory. If source is a file, target cannot be an existing directory.
`ln -s` source_file target	Create a symbolic link, i.e., an alias or short cut, from the source_file to the target. If the target is a file, it cannot exist. If the target is a directory, a file of same name as source_file cannot exist.
`mkdir` name	Make a directory of the given name. A file or directory of the given name cannot exist.
`rm` file ... `rm -r` directory `rmdir` directory	Remove files or directories. The first form removes one or more file(s). The second form recursively removes an entire directory hierarchy. The third form removes an empty directory.
`cd` directory	Change the current working directory to the given directory.
`pwd`	Print the current working directory.
`chmod` permissions file ... `chmod -R` permissions directory	Change the permissions mode of the given file(s) to the given permissions. The first form changes one or more files. The second form recursively changes all files in the given directory. The permissions argument is a octal number with values defined as follows: 0400 Allow read by owner. 0200 Allow write by owner. 0100 Allow execute (search in directory) by owner. 0700 Allow read, write, and execute (search) by owner. 0040 Allow read by group. 0020 Allow write by group. 0010 Allow execute (search in directory) by group. 0070 Allow read, write, and execute (search) by group. 0004 Allow read by others. 0002 Allow write by others. 0001 Allow execute (search in directory) by others. 0007 Allow read, write, and execute (search) by others.
`ls` `ls -sal`	List the contents of the current directory. The first form lists just the file names, not including files staring with ".". The second form gives a long-form listing of all files, including their sizes, modification dates, and permissions.
`man` command_name	Print the detailed manual page for the given command_name.
`gcc` file`.c` ...	Compile the given `.c` file(s), putting the executable result in the file named "`a.out`." See the `gcc` man page for the many options.
`gdb` executable_file	Run the executable_file under debugger control. E.g., gdb a.out runs the debugger on an `a.out` generated by `gcc`. See the `gdb` man page and 357 debugging handout for `gdb` command details.
`emacs` file ...	Launch the emacs editor on zero or more files. See the emacs man page for further details, including how to start the tutorial. (NOTE: On some terminals, you may have trouble with the backspace key, which Emacs uses as its help key. See the writeup for 357 Lab 1 to deal with this problem.)
command `>` output_file	Redirect the output of command to output_file. The command can be any valid UNIX call, including a compiled C program. E.g., a.out > outfile sends the standard output generated by the program `a.out` to the file named "`outfile`".
command `<` input_file	Redirect the contents of input_file to the input of command. The command can be any valid UNIX call, including a compiled C program. E.g., a.out < infile > outfile sends `infile` to the standard input of `a.out`, then sends the output to the file named "`outfile`".
command_1 `\|` command_2	Pipe the output of command_1 to the input of command_2. E.g., a.out \| fmt sends the output of `a.out` through the simple UNIX text formating command "`fmt` ".
command `\| tee` output_file	"Tee" the output of command to output_file, as well as to the normal standard output stream. E.g., a.out \| tee outfile sends the standard output of `a.out` to both `stdout` and the file named "`outfile`".
`>&` and `\|&`	These are forms of output redirection and piping that apply to `stderr` as well as `stdout`. E.g., a.out >& outfile redirects both the standard output and standard error of `a.out` to `outfile`. The command line a.out \|& tee outfile sends both standard output and standard error of `a.out` to their normal streams, as well as to `outfile`.

In the preceding commands, file and directory arguments are specified as a path name, in one of these forms:

a single name, referring to a file in the current directory
the period character, which stands for the current working directory
two period characters, which stands for the parent directory of the current working directory
two or more names separated by forward slashes, referring to a file in a sub(sub...)directory

A path that starts with a leading slash is an absolute path, referring to a file from the root of the entire file system. A path that starts with ~user_id is relative to the home directory of user whose UNIX ID is user_id. A tilde character by itself refers the current user's home directory.

Here are some examples of typical commands useful in CSC 357.

Example Command Description

cd
- or -
cd ~
Change to your home directory. Your home directory is the default when you initially log in, so this command is only necessary when you've used cd to change to some other directory.

mkdir cpe357
Make a directory named "cpe357".

chmod 700 cpe357
Change the permissions of cpe357 so that no one but you can access the files.

cd cpe357
Change into the cpe357 directory.

cp ~gfisher/classes/357/handouts/unix-commands.html .

Copy the file ~gfisher/classes/357/handouts/unix-commands.html into the current directory, i.e., cpe357.

rm unix-commands.html
Remove the unix-commands.html file -- you've decided to make a link instead.

ln -s ~gfisher/classes/357/handouts/unix-commands.html .

Make a symbolic link to ~gfisher/classes/357/handouts/unix- commands.html into the current directory. A symbolic link is the same as a short cut in Windows.

man ls
Print the manual page information for the ls command.

gcc -g lab1.c -o lab1
Compile lab1.c with a couple compiler options. The "-g" flag includes debugging information, so the executable program can be run better with gdb. The "-o" flag puts the executable program in the file named "lab1", instead of "a.out".

Example Command	Description
`cd` - or - `cd ~`	Change to your home directory. Your home directory is the default when you initially log in, so this command is only necessary when you've used `cd` to change to some other directory.
`mkdir cpe357`	Make a directory named "`cpe357`".
`chmod 700 cpe357`	Change the permissions of `cpe357` so that no one but you can access the files.
`cd cpe357`	Change into the `cpe357` directory.
`cp ~gfisher/classes/357/handouts/unix-commands.html .`	Copy the file `~gfisher/classes/357/handouts/unix-commands.html` into the current directory, i.e., `cpe357`.
`rm unix-commands.html`	Remove the unix-commands.html file -- you've decided to make a link instead.
`ln -s ~gfisher/classes/357/handouts/unix-commands.html .`	Make a symbolic link to `~gfisher/classes/357/handouts/unix- commands.html` into the current directory. A symbolic link is the same as a short cut in Windows.
`man ls`	Print the manual page information for the `ls` command.
`gcc -g lab1.c -o lab1`	Compile `lab1.c` with a couple compiler options. The "`-g`" flag includes debugging information, so the executable program can be run better with `gdb`. The "`-o`" flag puts the executable program in the file named "`lab1`", instead of "`a.out`".