base.sh

Shall高级编程

#!/bin/bash
###########################################################################
# Shellscript:	base.sh - print number to different bases (Bourne Shell)
# Author     :	Heiner Steven ([e-mail])
# Date       :	07-03-95
# Category   :	Desktop
# $Id: base.sh,v 1.2 2000/02/06 19:55:35 heiner Exp $
# ==> Above line is RCS ID info.
###########################################################################
# Description
#
# Changes
# 21-03-95 stv	fixed error occuring with 0xb as input (0.2)
###########################################################################

# ==> Used in ABS Guide with the script author's permission.
# ==> Comments added by ABS Guide author.

NOARGS=65
PN=`basename "$0"`			       # Program name
VER=`echo '$Revision: 1.2 $' | cut -d' ' -f2`  # ==> VER=1.2

Usage () {
    echo "$PN - print number to different bases, $VER (stv '95)
usage: $PN [number ...]

If no number is given, the numbers are read from standard input.
A number may be
    binary (base 2)		starting with 0b (i.e. 0b1100)
    octal (base 8)		starting with 0  (i.e. 014)
    hexadecimal (base 16)	starting with 0x (i.e. 0xc)
    decimal			otherwise (i.e. 12)" >&2
    exit $NOARGS 
}   # ==> Function to print usage message.

Msg () {
    for i   # ==> in [list] missing.
    do echo "$PN: $i" >&2
    done
}

Fatal () { Msg "$@"; exit 66; }

PrintBases () {
    # Determine base of the number
    for i      # ==> in [list] missing...
    do         # ==> so operates on command line arg(s).
	case "$i" in
	    0b*)		ibase=2;;	# binary
	    0x*|[a-f]*|[A-F]*)	ibase=16;;	# hexadecimal
	    0*)			ibase=8;;	# octal
	    [1-9]*)		ibase=10;;	# decimal
	    *)
		Msg "illegal number $i - ignored"
		continue;;
	esac

	# Remove prefix, convert hex digits to uppercase (bc needs this)
	number=`echo "$i" | sed -e 's:^0[bBxX]::' | tr '[a-f]' '[A-F]'`
	# ==> Uses ":" as sed separator, rather than "/".

	# Convert number to decimal
	dec=`echo "ibase=$ibase; $number" | bc`  # ==> 'bc' is calculator utility.
	case "$dec" in
	    [0-9]*)	;;			 # number ok
	    *)		continue;;		 # error: ignore
	esac

	# Print all conversions in one line.
	# ==> 'here document' feeds command list to 'bc'.
	echo `bc <<!
	    obase=16; "hex="; $dec
	    obase=10; "dec="; $dec
	    obase=8;  "oct="; $dec
	    obase=2;  "bin="; $dec
!
    ` | sed -e 's: :	:g'

    done
}

while [ $# -gt 0 ]
# ==>  Is a "while loop" really necessary here,
# ==>+ since all the cases either break out of the loop
# ==>+ or terminate the script.
# ==> (Above comment by Paulo Marcel Coelho Aragao.)
do
    case "$1" in
	--)     shift; break;;
	-h)     Usage;;                 # ==> Help message.
	-*)     Usage;;
         *)     break;;                 # first number
    esac   # ==> More error checking for illegal input might be useful.
    shift
done

if [ $# -gt 0 ]
then
    PrintBases "$@"
else					# read from stdin
    while read line
    do
	PrintBases $line
    done
fi


exit 0