X-Git-Url: https://git.phdru.name/?a=blobdiff_plain;f=docs%2Fmimedecode.rst;fp=docs%2Fmimedecode.rst;h=2e65036a3f9eb2da3ccdce98285ded7719e9df02;hb=53baf637d750e839121a6f217cdc8cf36dd81ed7;hp=0000000000000000000000000000000000000000;hpb=1bf81f1ddacccb164ccde9c34baf421d52bbb45f;p=mimedecode.git diff --git a/docs/mimedecode.rst b/docs/mimedecode.rst new file mode 100644 index 0000000..2e65036 --- /dev/null +++ b/docs/mimedecode.rst @@ -0,0 +1,355 @@ +Name +---- + +mimedecode -- decode MIME message + +Synopsis +-------- + +mimedecode [ -h|--help ] [ -V|--version ] [ -cCDP ] [ -f charset ] +[ -H|--host=hostname ] [ -d header1[,header2,header3...] ] +[ -d \*[,-header1,-header2,-header3...] ] +[ -p header1[,header2,header3,...]:param1[,param2,param3,...] ] +[ -p \*[,-header1,-header2,-header3,...]:param1[,param2,param3,...] ] +[ -p header1[,header2,header3,...]:\*[,-param1,-param2,-param3,...] ] +[ -p \*[,-header1,-header2,-header3,...]:\*[,-param1,-param2,-param3,...] ] +[ -r header1[,header2,header3...] ] [ -r \*[,-header1,-header2,-header3...] ] +[ -R header1[,header2,header3,...]:param1[,param2,param3,...] ] +[ -R \*[,-header1,-header2,-header3,...]:param1[,param2,param3,...] ] +[ -R header1[,header2,header3,...]:\*[,-param1,-param2,-param3,...] ] +[ -R \*[,-header1,-header2,-header3,...]:\*[,-param1,-param2,-param3,...] ] +[ --set-header header:value ] [ --set-param header:param=value ] +[ -BbeIit mask ] [ --save-headers|body|message mask ] [ -O dest_dir ] +[ -o output_file ] [input_file [output_file] ] + +DESCRIPTION +----------- + +Mail users, especially in non-English countries, often find that mail +messages arrived in different formats, with different content types, in +different encodings and charsets. Usually it is good because it allows to +use an appropriate format/encoding/whatever. Sometimes, though, some +unification is desirable. For example, one may want to put mail messages +into an archive, make HTML indices, run search indexer, etc. In such +situations converting messages to text in one character set and skipping +some binary attachments is much desirable. + +Here is a solution - mimedecode! + +This is a program to decode MIME messages. The program expects one input +file (either on command line or on stdin) which is treated as an RFC822 +message, and decodes to stdout or an output file. If the file is not an +RFC822 message it is just copied to the output one-to-one. If the file is +a simple RFC822 message it is decoded as one part. If it is a MIME message +with multiple parts ("attachments") all non-multipart subparts are +decoded. Decoding can be controlled by the command-line options. + +First, for every part the program removes headers and parameters listed +with -r and -R options. Then, Subject and Content-Disposition headers (and +all headers listed with -d and -p options) are examined. If any of those +exists, they are decoded according to RFC2047. Content-Disposition header +is not decoded (if it was not listed in option -d) - only its "filename" +parameter. Encoded header parameters violate the RFC, but widely deployed +anyway by ignorant coders who never even heard about RFCs. Correct +parameter encoding specified by RFC2231. This program decodes +RFC2231-encoded parameters, too. + +Then the body of the message (or the current part) is decoded. Decoding +starts with looking at header Content-Transfer-Encoding. If the header +specifies non-8bit encoding (usually base64 or quoted-printable), the body +is converted to 8bit (can be prevented with -B). Then if its content type +is multipart (multipart/related or multipart/mixed, e.g) every part is +recursively decoded. If it is not multipart, mailcap database is consulted +to find a way to convert the body to plain text (can be prevented with +options -Bbei). (The author has no idea how mailcap can be configured on +OSes other than POSIX, please don't ask; users can consult an example at +https://phdru.name/Software/dotfiles/mailcap.html). The decoding process +uses the first copiousoutput filter it can find. If there are no filters +the body just passed as is. + +Then Content-Type header is consulted for charset. If it is not equal to +the current locale charset and recoding is allowed (see options -Cc) the +body text is recoded. Finally message headers and the body are flushed to +stdout. + +Please be reminded that in the following options asterisk is a shell +metacharacter and should be escaped or quoted. Either write -d \*,-h1,-h2 +or -d '\*,-h1,-h2' or such. + +OPTIONS +------- + +-h, -help + + Print brief usage help and exit. + +-V, --version + + Print version and exit. + +-c + + Recode different character sets in message bodies to the current + default charset; this is the default. + +-C + + Do not recode character sets in message bodies. + +-f charset + + Force this charset to be used for recoding instead of charset from + the current locale. + +-H hostname, --host=hostname + + Use this hostname in X-MIME-Autoconverted headers instead of the + current hostname. + +-d header1[,header2,header3...] + + Add the header(s) to a list of headers to decode; initially the + list contains headers "From", "To", "Cc", "Reply-To", + "Mail-Followup-To" and "Subject". + +-d \*[,-header1,-header2,-header3...] + + This variant completely changes headers decoding. First, the list + of headers to decode is cleared (as with -D). Then all the headers + are decoded except the given list of exceptions (headers listed + with '-'). In this mode it would be meaningless to give more than + one -d options but the program doesn't enforce the limitation. + +-D + + Clear the list of headers to decode (make it empty). + +-p header1[,header2,header3,...]:param1[,param2,param3,...] + + Add the parameter(s) to a list of headers parameters to decode; + the parameter(s) will be decoded only for the given header(s). + Initially the list contains header "Content-Type", parameter + "name"; and header "Content-Disposition", parameter "filename". + +-p \*[,-header1,-header2,-header3,...]:param1[,param2,param3,...] + + Add the parameter(s) to a list of headers parameters to decode; + the parameter(s) will be decoded for all headers except the given + ones. + +-p header1[,header2,header3,...]:\*[,-param1,-param2,-param3,...] + + Decode all parameters except listed for the given list of headers. + +-p \*[,-header1,-header2,-header3,...]:\*[,-param1,-param2,-param3,...] + + Decode all parameters except listed for all headers (except + listed). + +-P + + Clear the list of headers parameters to decode (make it empty). + +-r header1[,header2,header3...] + + Add the header(s) to a list of headers to remove completely; + initially the list is empty. + +-r \*[,-header1,-header2,-header3...] + + Remove all headers except listed. + +-R header1[,header2,header3,...]:param1[,param2,param3,...] + + Add the parameter(s) to a list of headers parameters to remove; + the parameter(s) will be removed only for the given header(s). + Initially the list is empty. + +-R \*[,-header1,-header2,-header3,...]:param1[,param2,param3,...] + +-R header1[,header2,header3,...]:\*[,-param1,-param2,-param3,...] + +-R \*[,-header1,-header2,-header3,...]:\*[,-param1,-param2,-param3,...] + + Remove listed parameters (or all parameters except listed) from + these headers (or from all headers except listed). + +--set-header header:value + + The program sets or changes value for the header to the given + value (only at the top-level message). + +--set-param header:param=value + + The program sets or changes value for the header's parameter to + the given value (only at the top-level message). The header must + exist. + +-B mask + + Append mask to the list of binary content types that will be not + content-transfer-decoded (will be left as base64 or such). + +-b mask + + Append mask to the list of binary content types; if the message to + decode has a part of this type the program + content-transfer-decodes (base64 or whatever to 8bit binary) it + and outputs the decoded part as is, without any further + processing. + +-e mask + + Append mask to the list of error content types; if the message to + decode has a part of this type the program fails with ValueError. + +-I mask + + Append mask to the list of content types to completely ignore. + There will be no output - no headers, no body, no warning. For a + multipart part the entire subtree is removed. + +-i mask + + Append mask to the list of content types to ignore; if the message + to decode has a part of this type the program outputs headers but + skips the body. Instead a line "Message body of type %s skipped." + will be issued. + +-t mask + + Append mask to the list of content types to convert to text; if + the message to decode has a part of this type the program consults + mailcap database, find the first copiousoutput filter and, if any + filter is found, converts the part. + +--save-headers mask + +--save-body mask + +--save-message mask + + Append mask to lists of content types to save to files; + --save-headers saves only decoded headers of the message (or the + current subpart); --save-body saves only decoded body; + --save-message saves the entire message or subpart (headers + + body). + +-O dest_dir + + Set destination directory for the output files; if the directory + doesn't exist it will be created. Default is the current + directory. + +-o output_file + + Save output to the file related to the destination directory from + option -O. Also useful in case of redirected stdin: + +mimedecode -o output_file < input_file +cat input_file | mimedecode -o output_file + +The 5 list options (-Bbeit) require more explanation. They allow a user to +control body decoding with great flexibility. Think about said mail +archive; for example, its maintainer wants to put there only texts, +convert PDF/Postscript to text, pass HTML and images decoding base64 to +html but leaving images encoded, and ignore everything else. This is how +it could be done: + +mimedecode -t application/pdf -t application/postscript -t text/plain -b +text/html -B 'image/\*' -i '\*/\*' + +When the program decodes a message (non-MIME or a non-multipart subpart of +a MIME message), it consults Content-Type header. The content type is +searched in all 5 lists, in order "text-binary-ignore-error". If found, +appropriate action is performed. If not found, the program searches the +same lists for "type/\*" mask (the type of "text/html" is just "text"). If +found, appropriate action is performed. If not found, the program searches +the same lists for "\*/\*" mask. If found, appropriate action is performed. +If not found, the program uses the default action, which is to decode +everything to text (if mailcap specifies a filter). This algorithm allows +more specific content types to override less specific: -b image/\* will be +processed earlier than -B \*/\*. + +Options -e/-I/-i can also work with multipart subparts of a MIME message. +In case of -I/-i the entire subtree of that multipart is removed; with -i +it's replaced with ignore warning. + +Initially all 5 lists are empty, so without any additional parameters the +program always uses the default decoding (as -t \*/\*). + +The 3 save options (--save-headers/body/message) are similar. They make +the program to save every non-multipart subpart (only headers, or body, or +the entire subpart: headers + body) that corresponds to the given mask to +a file. Before saving the message (or the subpart) is decoded according to +all other options and is placed to the output stream as usual. Filename +for the file is created using "filename" parameter from the +Content-Disposition header, or "name" parameter from the Content-Type +header if one of those exist; a serial counter is prepended to the +filename to avoid collisions; if there are no name/filename parameters, or +the name/filename parameters contain forbidden characters (null, slash, +backslash) the filename is just the serial counter. + +If the file doesn't have any extensions (no dots in the value of the +name/filename parameters, or the name is just the counter) the program +tries to guess an extension by looking up the content type in mime.types +files including .mime.types file in the user's home directory (if it +exists). If the file has an extension the program doesn't try to verify +that it corresponds to the content type. + +The file is saved in the directory set with -O (default is the current +directory). The save options are proceeded before -e options so the user +can save the message that causes an error. + +ENVIRONMENT +----------- + +LANG + +LC_ALL + +LC_CTYPE + +Define current locale settings. Used to determine current default charset +(if your Python is properly installed and configured). + +BUGS +---- + +The program may produce incorrect MIME message. The purpose of the program +is to decode whatever it is possible to decode, not to produce absolutely +correct MIME output. The incorrect parts are obvious - decoded +From/To/Cc/Reply-To/Mail-Followup-To/Subject headers and filenames. Other +than that output is correct MIME message. The program does not try to +guess whether the headers are correct. For example, if a message header +states that charset is iso8859-1, but the body (HTML, for example) is +actually in utf-8 the program will recode the message with the wrong +charset. + +AUTHOR +------ + +Oleg Broytman + +COPYRIGHT +--------- + +Copyright (C) 2001-2020 PhiloSoft Design. + +LICENSE +------- + +GNU GPL + +NO WARRANTIES +------------- + +This program is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY +or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +for more details. + +SEE ALSO +-------- + +mimedecode home page: https://phdru.name/Software/Python/#mimedecode