RHCSA notes

 BASICS OF LINUX YOU 

whomi [opt.]

                  Print the user name associated with the current effective user ID.

-The control of users and groups is a core element of Linux system administration.

-There are three types of user in linux: - root, regular and service.

pwd [opt] 

 Print the name of the current working directory.

1. -L        print the value of $PWD if it names the current working

                directory

2. -P        print the physical directory, without any symbolic links.

touch

Update the access and modification times of each FILE to the current time.

  -a                                 change only the access time

  -c, --no-create             do not create any files

  -d, --date=STRING      parse STRING and use it instead of current time

  -h, --no-dereference   affect each symbolic link instead of any referenced

                                       file (useful only on systems that can change the

                                       timestamps of a symlink)

  -m                                 change only the modification time

  -r, --reference=FILE     use this file's times instead of current time

  -t STAMP                      use [[CC]YY]MMDDhhmm[.ss] instead of current time

      --time=WORD          change the specified time:

                                      WORD is access, atime, or use: equivalent to -a

                                      WORD is modify or mtime: equivalent to -m

cat

Concatenate FILE(s) to standard output.

 -A, --show-all                   equivalent to -vET

  -b, --number-nonblank    number nonempty output lines, overrides -n

  -e                                    equivalent to -vE

  -E, --show-ends             display $ at end of each line

  -n, --number                   number all output lines

  -s, --squeeze-blank       suppress repeated empty output lines

  -t                                    equivalent to -vT

  -T, --show-tabs              display TAB characters as ^I

vi

edit specified file(s)

read text from stdin

edit file where tag is defined

edit file with first error

 --                   Only file names after this

   -v                   Vi mode (like "vi")

   -e                   Ex mode (like "ex")

   -E                   Improved Ex mode

   -s                   Silent (batch) mode (only for "ex")

   -d                   Diff mode (like "vimdiff")

   -y                   Easy mode (like "evim", modeless)

   -R                   Readonly mode (like "view")

   -Z                   Restricted mode (like "rvim")

   -m                   Modifications (writing files) not allowed

   -M                   Modifications in text not allowed

   -b                   Binary mode

   -l                   Lisp mode

   -C                   Compatible with Vi: 'compatible'

   -N                   Not fully Vi compatible: 'nocompatible'

   -V[N][fname]         Be verbose [level N] [log messages to fname]

   -D                   Debugging mode

   -n                   No swap file, use memory only