This is first time that I am using Linux, and I need to understand some concepts about two commands. I would be happy if you could explain the process one by one.
What does this command do?
cat ../test And what does this command do?
cat /etc/shadow 2>&1 | wc -l Thank you!
"../" is the parent directory.
So "cat ../test" means "print the 'test' file located in parent directory to standard output."
Second question:
All Linux (and Unix) processes have 3 standard files.
File 0 is input (stdin).
File 1 is normal output (stdout).
File 2 is error output (stderr).
2&>1 means "transfer error output into standard output".
The pipe | means "transfer output to the input of another program"
And the whole line means "count and display number of lines in /etc/shadow (including error messages if any).
You probably know what the cat command does. The man page states:
cat - concatenate files and print on the standard output
../ means the parent directory of your current working directory. So, if there is a file called test at that location the cat command will print it for you on the terminal.
In the second example, the content of /etc/shadow (if you have access to), will be piped to wc command.
wc - print newline, word, and byte counts for each file
-l, --lines: print the newline counts
This will print the number of lines in /etc/shadow on the terminal (only the number of lines, not the content). The 2>&1 notation redirects file descriptor 2 (standard error) to file descriptor 1 (standard output).
