Maths : What is a Function : y=f(x)

commandline session and notes related
may be engineering functions related.
suppose y=f(x).
y = output.
suppose i equate y to ls
ls is a	GNU command.
ls contains different methods(ingredients) which form ls command.
suppose	i write	 ls = f (-a,-i,-l,...)
different cases	:
1. y = -a
2. y = -al
3. y = -l,
4. y = -i
5. y = -ail



$ls -ail
total 1708
3673124 drwxr-xr-x  4 jeffrin jeffrin    4096 Nov 27 20:18 .
3670018 drwxr-xr-x 48 jeffrin jeffrin    4096 Nov 27 19:13 ..
3804877 drwxr-xr-x  2 jeffrin jeffrin    4096 Nov 22 21:40 direct
3670534 lrwxrwxrwx  1 jeffrin jeffrin       7 Nov 22 21:41 directlink -> direct/
3673719 -rw-r--r--  1 jeffrin jeffrin     104 Nov 15 20:50 file
3805205 drwx------  2 jeffrin jeffrin    4096 Nov 25 20:18 Mail
3671094 -rw-r--r--  1 jeffrin jeffrin 1710918 Nov 25 02:23 out.ogv
3673430 -rw-r--r--  1 jeffrin jeffrin    7946 Nov 25 01:55 shelr-record.json
3673230 -rw-r--r--  1 jeffrin jeffrin     217 Nov 27 20:16 tmp
3672617 lrwxrwxrwx  1 jeffrin jeffrin      30 Nov 27 20:18 .#tmp -> jeffrin@debian.5024:1385559781
3673193 -rw-r--r--  1 jeffrin jeffrin       1 Nov 27 19:54 tmp~
$ls -a
.  ..  direct  directlink  file  Mail  out.ogv  shelr-record.json  tmp  .#tmp  tmp~
$ls -i
3804877 direct      3673719 file  3671094 out.ogv            3673230 tmp
3670534 directlink  3805205 Mail  3673430 shelr-record.json  3673193 tmp~
$ls -l
total 1700
drwxr-xr-x 2 jeffrin jeffrin    4096 Nov 22 21:40 direct
lrwxrwxrwx 1 jeffrin jeffrin       7 Nov 22 21:41 directlink -> direct/
-rw-r--r-- 1 jeffrin jeffrin     104 Nov 15 20:50 file
drwx------ 2 jeffrin jeffrin    4096 Nov 25 20:18 Mail
-rw-r--r-- 1 jeffrin jeffrin 1710918 Nov 25 02:23 out.ogv
-rw-r--r-- 1 jeffrin jeffrin    7946 Nov 25 01:55 shelr-record.json
-rw-r--r-- 1 jeffrin jeffrin     217 Nov 27 20:16 tmp
-rw-r--r-- 1 jeffrin jeffrin       1 Nov 27 19:54 tmp~
$