Unix Day5 Commands

cat
program concatenates the contents of files, reading from a list of files and/or standard input in sequence and writing their contents in order to standard output. cat takes the list of files as arguments but also interprets the argument "-" as standard input.
Example: cat filename

who
The Unix command who displays a list of users who are currently logged into a computer. The command accepts various options that vary by system to further specify the information that is returned, such as the length of time a particular user has been connected or what pseudo-teletype a user is connected to. The who command is related to the command w, which provides the same information but also displays additional data and statistics.
Example output
user19 pts/35 Apr 18 08:40 (localhost)
user28 pts/27 Apr 18 09:50 (localhost)

Unix Day4 Commands

find
program is a search utility, mostly found on Unix-like platforms. It searches through a directory tree of a filesystem, locating files based on some user-specified criteria. By default, find returns all files below the current working directory. Further, find allows the user to specify an action to be taken on each matched file. Thus, it is an extremely powerful program for applying actions to many files. It also supports regexp matching.
Examples
From current directory
This searches in the current directory (represented by a period) and below it, for files and directories with names starting with my. The backslash before the star is needed to avoid the shell expansion. Without the backslash, the shell would replace my* with the list of files whose names begin with my in the current directory. An alternative is to enclose the the arguments in quotes: find . -name "my*"
Files only find . -name "my*" -type f This limits the results of the above search to only regular files, therefore excluding directories, special files, pipes, symbolic links, etc. my* is enclosed in quotes as otherwise the shell would replace it with the list of files in the current directory starting with my echo is a command in Unix (and by extension, its descendants, such as Linux) and MS-DOS that places a string on the terminal. It is typically used in shell scripts and batch programs to output status text to the screen or a file. $ echo This is a test. This is a test. $ echo "This is a test." > ./test.txt $ cat ./test.txt This is a test.

Unix Day3 Commands

rmdir
is a command which will remove an empty directory on a Unix-system. It cannot be capitalized. Normal usage is straightforward where one types:
rmdir name_of_directory
Where name_of_directory corresponds with the name of the directory one wishes to delete. There are options to this command such as -p which removes parent directories if they are also empty.
For example:
rmdir –p foo/bar/baz
Will first remove baz/, then bar/ and finally foo/ thus removing the entire directory tree specified in the command argument.
Often rmdir will not remove a directory if there is still files present in the directory. To force the removal of the directory even if files are present usually the -rf flag can be used. For example:
rmdir -Rf for/bar/baz

cp
is the command entered in a Unix shell to copy a file from one place to another, possibly on a different filesystem. The original file remains unchanged, and the new file may have the same or a different name.
To Copy a File to another File
cp [ -f ] [ -h ] [ -i ] [ -p ][ -- ] SourceFile TargetFile

To Copy a File to a Directory
cp [ -f ] [ -h ] [ -i ] [ -p ] [ -r | -R ] [ -- ] SourceFile ... TargetDirectory

To Copy a Directory to a Directory
cp [ -f ] [ -h ] [ -i ] [ -p ] [ -- ] { -r | -R } SourceDirectory ... TargetDirectory

-f (force) – specifies removal of the target file if it cannot be opened for write operations. The removal precedes any copying performed by the cp command.
-h – makes the cp command copy symbolic links. The default is to follow symbolic links, that is, to copy files to which symbolic links point.
-i (interactive) – prompts you with the name of a file to be overwritten. This occurs if the TargetDirectory or TargetFile parameter contains a file with the same name as a file specified in the SourceFile or SourceDirectory parameter. If you enter y or the locale's equivalent of y, the cp command continues. Any other answer prevents the cp command from overwriting the file.
-p (preserve) – duplicates the following characteristics of each SourceFile/SourceDirectory in the corresponding TargetFile and/or TargetDirectory:

Unix Day2 Commands

mkdir
command in the Unix operating system is used to make a new Directory. Normal usage is as straightforward as follows:
mkdir name_of_directory
Where name_of_directory is the name of the directory one wants to create. When typed as above (ie. normal usage), the new directory would be created within the current directory.

rm (short for remove)
is a Unix command used to delete files from a filesystem. Common options that rm accepts include :
-r, which processes subdirectories recursively
-i, which asks for every deletion to be confirmed
-f, which ignores non-existent files and overrides any confirmation prompts ("force")
"rm -rf" (variously, "rm -rf /", "rm -rf *", and others) is frequently used in jokes and anecdotes about Unix disasters. The "rm -rf /" variant of the command, if run by an administrator, would cause the contents of every mounted disk on the computer to be deleted.