touch cat vi differences

Use vi to edit an existing file or to create a new, empty one and edit it immediately.

Use cat to create a new file from an existing one or to concatenate two or more files to a new one, or to append two or more files to an existing one.

Use touch to create a new, empty file or to update the last modified date of an existing file.

cat and touch does same things?

Please re-read my answer!
cat and touch  c a n  do the same (if you "cat" an empty file into a new one an empty file is created), but cat isn't really meant for this (see above).
touch, on the other hand, never writes content to a file, it changes its date (and creates it, if not present).

>> Also always use full path.
Here goes exceptions because of not using full path.

Initially doing unalias for ls command and redirecting the error (if any) to /dev/null

$ unalias ls 2>/dev/null

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Writing a sample function for ls:

$ unset -f ls
$ ls ()
{
           echo "Use full path instead of using ls command"
           echo "/bin/ls $@"
           Ret=13
           return $Ret
}
$ ls /home/MurugesanDinesh
Use full path instead of using ls command
/bin/ls /home/MurugesanDinesh
$ echo "Return value of previous ls command is [ $? ] which needs to be 13 since we have written 13 in ls function"
Return value of previous ls command is [ 13 ] which needs to be 13 since we have written 13 in ls function
$ echo "Return value of previous echo command is [ $? ] which needs to be 0 since we have used expected output of echo command"
Return value of previous echo command is [ 0 ] which needs to be 0 since we have used expected output of echo command

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