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uuencode, uudecode - encode a binary file, or decode its representation


uuencode [-m] [ file ] name

uudecode [-o outfile] [ file ]...


Uuencode and uudecode are used to transmit binary files over transmission mediums that do not support other than simple ASCII data.

Uuencode reads file (or by default the standard input) and writes an encoded version to the standard output. The encoding uses only printing ASCII characters and includes the mode of the file and the operand name for use by uudecode. If name is /dev/stdout the result will be written to standard output. By default the standard UU encoding format will be used. If the option -m is given on the command line base64 encoding is used instead.

Note: uuencode uses buffered input and assumes that it is not hand typed from a tty. The consequence is that at a tty, you may need to hit Ctl-D several times to terminate input.

Uudecode transforms uuencoded files (or by default, the standard input) into the original form. The resulting file is named name (or outfile if the -o option is given) and will have the mode of the original file except that setuid and execute bits are not retained. If outfile or name is /dev/stdout the result will be written to standard output. Uudecode ignores any leading and trailing lines. The program can automatically decide which of the both supported encoding schemes are used.


The following example packages up a source tree, compresses it, uuencodes it and mails it to a user on another system. When uudecode is run on the target system, the file ‘’src_tree.tar.Z’’ will be created which may then be uncompressed and extracted into the original tree.

tar cf - src_tree | compress | uuencode src_tree.tar.Z | mail sys1!sys2!user

See Also

compress(1) , mail(1) , uucp(1) , uuencode(5)


This implementation is compliant with P1003.2b/D11.


If more than one file is given to uudecode and the -o option is given or more than one name in the encoded files are the same the result is probably not what is expected.

The encoded form of the file is expanded by 37% for UU encoding and by 35% for base64 encoding (3 bytes become 4 plus control information).

Reporting Bugs

Report bugs to <>. Please put sharutils or uuen_code in the subject line. It helps to spot the message.


The uuencode command appeared in BSD 4.0.

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