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# Rolling anything what you want.
# arg1: text to roll.
# arg2: max length to display.
# arg3: roll speed in characters per second.
roll_text() {
local text="$1" # Text to print
if [ -z "$text" ]; then
return;
fi
local max_len="10" # Default max length.
if [ -n "$2" ]; then
max_len="$2"
fi
local speed="1" # Default roll speed in chars per second.
if [ -n "$3" ]; then
speed="$3"
fi
# Skip rolling if the output is less than max_len.
if [ "${#text}" -le "$max_len" ]; then
echo "$text"
return
fi
# Anything starting with 0 is an Octal number in Shell,C or Perl,
# so we must explicitly state the base of a number using base#number
local offset=$((10#$(date +%s) * ${speed} % ${#text}))
# Truncate text.
text=${text:offset}
local char # Character.
local bytes # The bytes of one character.
local index
for ((index=0; index < max_len; index++)); do
char=${text:index:1}
bytes=$(echo -n $char | wc -c)
# The character will takes twice space
# of an alphabet if (bytes > 1).
if ((bytes > 1)); then
max_len=$((max_len - 1))
fi
done
text=${text:0:max_len}
#echo "index=${index} max=${max_len} len=${#text}"
# How many spaces we need to fill to keep
# the length of text that will be shown?
local fill_count=$((${index} - ${#text}))
for ((index=0; index < fill_count; index++)); do
text="${text} "
done
echo "${text}"
}
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