Miscellaneous short note on Linux. Part -4

# uptime --- It shows since how long system is running and the number of user are  currently logged in and also displays load average for 1, 5 and 15 minutes intervals

# Three types of owner of file or directory
(i)                 User or creator of the file
(ii)               Group [All user belonging in the group have the same file permission]
(iii)             Other [Any other user who has access permission to a file. Other does not own the file not belong to the group]

 # ls –l and ls –la are not same.

# Using the “pr” command you can format and print a file directly from the terminal. The formatting you do on the files does not affect the file content.

# standard input (stdin) device is the keyboard

# standard output (stdout)  device is the monitor

# “>” symbol is used for output (stdout) redirection to another file. If the file with the same name exist then the previous file will be over written.

# echo hello > listing --- listing life content will be hello

# “>>” symbol is used to add content to the existing file. It will not overwrite the content of the existing file.

# “<” symbol is used for input (stdin) redirection.

# every file has a number called FD.

# whenever you execute a program or command, three files are always open.
(i)                 Standard input --- FD 0
(ii)               Standard output --- FD 1
(iii)             Standard error --- FD 2

# “>&” which write the output from one file to the input of another file.

# Each file in linux has a corresponding file descriptor associated with it.

# You can redirect error using it’s corresponding file descriptor 2

# find --- To search in a specific directory for a file