ell. If the file argument to one of the primaries is of the form `/dev/fd/N', then file descriptor N is checked. If the file argument to one of the primaries is one of `/dev/stdin', `/dev/stdout', or `/dev/stderr', file descriptor 0, 1, or 2, respectively, is checked.
-a file
True if file exists.
-b file
True if file exists and is a block special file.
-c file
True if file exi
o restore the echoing, use stty echo. However, it is poor programming to make the assumption that echo is on. In some cases, echoing of characters is done ... l appear twice.
To avoid this, a neat stty trick is used in which the original state of stty is stored before the stty change and restored after
