btoa(1)

NAME

btoa, atob, tarmail, untarmail - encode/decode binary to printable ASCII

SYNOPSIS

btoa
atob
tarmail [ -u ] who subject files ...
untarmail [ file ]

DESCRIPTION

btoa is a filter that reads anything from the standard input, and encodes it into printable ASCII on the standard output. It also attaches a header and checksum information used by the reverse filter atob to find the start of the data and to check integrity.

Atob reads an encoded file, strips off any leading and trailing lines added by mailers, and recreates a copy of the the standard output. Atob gives NO output and exits with an error message if its input is garbage or the checksums do not check.

Tarmail is a shell script that tar’s up all the given files, pipes them through compress, btoa, and mails them to the given person with the given subject phrase.

For example:

tarmail ralph "here it is ralph" foo.c a.out

will package up files foo.c and a.out and mail them to ralph using subject here it is ralph. Notice the quotes on the subject. They are necessary to make it one argument to the shell.

The -u option to tarmail is specific to CX/UX and will cause tar to archive the given file name arguments utilizing a format recognized by versions of tar distributed by the University of California at Berkeley (UCB). UCB tar historically appends a slash (/) by default to the end of all directory names archived. The / is used by UCB tar to determine whether a directory is being extracted from the archive. The CX/UX version of tar used in tarmail complies with the POSIX 1003.1 and X/Open extended tar format which does not permit the UCB tar default action. As a result, CX/UX tarmail archives sent to pre-CX/UX 5.3 and non-CX/UX systems which utilize the UCB tar will not be readable when untarmail or tar is used on them. Utilizing this option will cause CX/UX tar to perform the UCB default action.

Tarmail with no args will print a short message reminding you what the required args are. When the mail is received at the other end, that person should use mail to save the message in some temporary file name (say xx). Then saying untarmail xx will decode the message and untar it. Untarmail can also be used as a filter. By using tarmail, binary files and entire directory structures can be easily transmitted between machines. Naturally, you should understand what tar itself does before you use tarmail.

Other uses:

compress < secrets | crypt | btoa | mail ralph

will mail the encrypted contents of the file secrets to ralph. If ralph knows the encryption key, he can decode it by saving the mail (say in xx), and then running:

atob < xx | crypt | uncompress

(crypt requests the key from the terminal, and the secrets come out on the terminal).

AUTHOR

Paul Rutter (modified by Joe Orost)

FEATURES

btoa uses a compact base-85 encoding so that 4 bytes are encoded into 5 characters (file is expanded by 25%). As a special case, 32-bit zero is encoded as one character. This encoding produces less output than uuencode(1C).

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