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~ $