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Full Discussion: Check if a variable is zero
Top Forums Shell Programming and Scripting Check if a variable is zero Post 302480698 by jim mcnamara on Wednesday 15th of December 2010 02:00:16 PM
Old 12-15-2010
Those numbers, if they were treated as number or hex numbers overflow the limits of POSIX shell arithmetic. However strings are different.
Code:
#!/bin/ksh
iszero()   # print 1 if zero,  0 else
{
     ok=$(echo "$1" | tr -d '0')
     if [ -z "$ok" ] ; then
        print 1
     else
        print 0
     fi
}
a=574E47303030303030303030303030303030303135313937
b=000000000000000000000000000000000000000000000000
echo "$a  result: $(iszero $a)"
echo "$b  result: $(iszero $b)"

 

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SORT(1) 						      General Commands Manual							   SORT(1)

NAME
sort - sort a file of ASCII lines SYNOPSIS
sort [-bcdfimnru] [-tc] [-o name] [+pos1] [-pos2] file ... OPTIONS
-b Skip leading blanks when making comparisons -c Check to see if a file is sorted -d Dictionary order: ignore punctuation -f Fold upper case onto lower case -i Ignore nonASCII characters -m Merge presorted files -n Numeric sort order -o Next argument is output file -r Reverse the sort order -t Following character is field separator -u Unique mode (delete duplicate lines) EXAMPLES
sort -nr file # Sort keys numerically, reversed sort +2 -4 file # Sort using fields 2 and 3 as key sort +2 -t: -o out # Field separator is : sort +.3 -.6 # Characters 3 through 5 form the key DESCRIPTION
Sort sorts one or more files. If no files are specified, stdin is sorted. Output is written on standard output, unless -o is specified. The options +pos1 -pos2 use only fields pos1 up to but not including pos2 as the sort key, where a field is a string of characters delim- ited by spaces and tabs, unless a different field delimiter is specified with -t. Both pos1 and pos2 have the form m.n where m tells the number of fields and n tells the number of characters. Either m or n may be omitted. SEE ALSO
comm(1), grep(1), uniq(1). SORT(1)
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