Linux Commands Part 1 - 4
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Tags: linux-com-book
# before terminal means super-user
date to print date and time
Sat Jun 18 12:01:17 AM IST 2022
cal to print calendar
df to print disk drive and usage
free to print memory
pwd print working directory
Absolute PathName : begins with root directory and follows the tree branch by branch till the desired folder
Relative PathName : starts from the working directory
cd to change directory
cd - to revert to previous directory
cd ~username : to change directory to another user
ls : to list directories
ls directory_1 directory_2 : to print list or multiple directories
ls -l : for more details
ls -lt : to list sorted acc. date modifed
—reverse : to reverse the sort
Long Listing Details
file filename : to print a brief description of the file’s contents
less : to view content of file
symbolic links are like aliases or another name for the file
Why they are useful ?
Imagine we have a file with name foo . Whenever we update it we, change its name to foo-date-time, but the programs/user referencing it wouldst know that the name has change. To tackle this problem, we create a symlink of file foo → foo-date-time and the programs/user user only reference the symlink.
So even if we change the name of file foo, it wont affect the programs as they would be referencing the symlink.
to create new directories
mkdir dir_name
to create multiple directories
mkdir dir1 dir2 dir3
to copy file to another directory
cp item directory
if cp item1 item2 then content of item2 is replace with item1
use -a file while copying to copy the attributes as well
The mv command performs both file moving and file renaming, depending on how it is used
to move item to another directory mv item... directory
to delete item rm item
Hard links are the original Unix way of creating links
Every file has a single hard link that gives the file its name
Limitations
A hard link cannot reference a file outside its own file system
A hard link may not reference a directory
A hard link is indistinguishable from the file itself
They work by creating a special type of file that contains a text pointer to the referenced file or directory
They are like windows shortcuts
If file is deleted, then link points to nothing, it is broken
