Передача бинарных файлов текстом¶

Декодировщик средствами bash¶

base64decode.sh

#!/bin/bash

 # Base64 decoding routine written entirely in bash, with no external dependencies. 
 #
 # Usage:
 # base64decode < input > output
 #
 # This code is absurly inefficient; it runs aproximately 12,000 times slower than
 # the perl-based decoder. The difference is that this code doesn't require you to
 # install any external programs, which may be important in some cases.
 #
 # To decode using perl instead, use the following:
 # 
 # base64decode() {
 # perl -e 'use MIME::Base64 qw(decode_base64);$/=undef;print decode_base64(<>);'
 # }
 #

 base64decode() {
     L=0
     A=0
     P=0
     while read -n1 C ; do
         printf -v N %i \'"$C" 
         if (( $N == 61 )) ; then
             P=$(( $P + 1 )) # = (padding)
             V=0
         elif (( $N == 43 )) ; then
             V=62 # +
         elif (( $N == 47 )) ; then
             V=63 # /
         elif (( $N < 48 )) ; then
             continue
         elif (( $N < 58 )) ; then
             V=$(( $N + 4 )) # -48 + 52 (0-9)
         elif (( $N < 65 )) ; then
             continue
         elif (( $N < 91 )) ; then
             V=$(( $N - 65 )) # -65 + 0 (A-Z)
         elif (( $N < 97 )) ; then
             continue
         elif (( $N < 123 )) ; then
             V=$(( $N - 71 )) # -97 + 26 (a-z)
         else
             continue
         fi

         A=$(( ($A << 6) | $V ))
         L=$(( $L + 1 )) 

         if [ $L == 4 ] ; then
             printf -v X "%x" $(( ($A >> 16) & 0xFF ))
             printf "\x$X" 
             if (( $P < 2 )) ; then
                 printf -v X "%x" $(( ($A >> 8) & 0xFF ))
                 printf "\x$X" 
             fi
             if (( $P == 0 )) ; then
                 printf -v X "%x" $(( $A & 0xFF ))
                 printf "\x$X" 
             fi 
             A=0
             L=0
             P=0
         fi
     done
 }

base64decode