2.1.5 Protecting against transmission errors

Transmission of shell archives is not always free of errors. So one should make consistency checks on the receiving site. A very simple (and unreliable) method is running the UNIX wc tool on the output file. This can report the number of characters in the file.

As one can guess this does not catch all errors. Especially changing of a character value does not change the computed check sum. To achieve this goal better method were invented and standardized. One very strong is MD5 (MD = message digests). This is standardized in RFC 1321. The produced shell scripts do not force the md5sum program to be installed on the system. This is necessary because it is not yet part of every UNIX. The program is however not necessary for producing the shell archive.

-w

--no-character-count

Do not check with `wc -c' after unpack. The default is to check.

-D

--no-md5-digest

Do not check with `md5sum' after unpack. The default is to check.

-F

--force-prefix

Prepend the prefix character to every line even if not required. This option may slightly increase the size of the archive, especially if -B or -Z is used. Normally, the prefix character is `X'. If the parameter to the -d option starts with `X', then the prefix character becomes `Y'.

-d string

--here-delimiter=string

Use string to delimit the files in the shar instead of `SHAR_EOF'. This is for those who want to personalize their shar files.

This document was generated by Bruce Korb on June, 3 2006 using texi2html 1.76.