. 1, echo
a.echo plus>, may be redirected to a file which the string
2, CAT
A role: the contents of the file can be viewed
b.cat/dev/null> filename filename can redirect the file is empty file
. 3, More
A role: to display its contents
. B View down: spacebar, F
C up view: B
. D view which file is ": F"
. exit is E "Q"
f.more + (NUM ) number of lines from the filename of the file filename num begin viewing
. 4, less
a role: to view the file content
b.pageup & pagedown to flip
. 5, head
a to view the contents of the file header, the default line 10.
b.head -n [num] filename filename of the file from the head start showing num lines
6, tail
a. tail view the contents of the file, the default 10 lines
b.tail -n [num] filename filename of the file from the tail began to show num lines
c.tail -f filename to create a foreground process ctrl + c
download tree: sudo yum -y install tree
