GNU shar utilities: 2.1.5 Protecting against transmission errors

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### 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 March, 25 2006 using texi2html 1.76.