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Homework and Emergencies Homework & Coursework Questions Help with bash shell scripting Post 302513199 by DGPickett on Tuesday 12th of April 2011 02:41:56 PM
Old 04-12-2011
But then it might not be ksh portable!
Code:
$ echo "(( 1 + 2 ))"
(( 1 + 2 ))
$ echo (( 1 + 2 ))  
ksh: syntax error: `((' unexpected
$ echo $(( 1 + 2 ))
3
$

Integer limited 31 bit signed, not much error checking:
Code:
$ z=1;while [ 1 ]
do
echo $z
z=$(( $z + $z ))
done 2>&1|pg
1
2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
65536
131072
262144
524288
1048576
2097152
4194304
8388608
16777216
33554432
67108864
134217728
268435456
536870912
1073741824
-2147483648
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

 

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echo(3XCURSES)						  X/Open Curses Library Functions					    echo(3XCURSES)

NAME
echo, noecho - enable/disable terminal echo SYNOPSIS
cc [ flag... ] file... -I /usr/xpg4/include -L /usr/xpg4/lib -R /usr/xpg4/lib -lcurses [ library... ] c89 [ flag... ] file... -lcurses [ library... ] #include <curses.h> int echo(void); int noecho(void); DESCRIPTION
The echo() function enables Echo mode for the current screen. The noecho() function disables Echo mode for the current screen. Initially, curses software echo mode is enabled and hardware echo mode of the tty driver is disabled. The echo() and noecho() functions control soft- ware echo only. Hardware echo must remain disabled for the duration of the application, else the behavior is undefined. RETURN VALUES
Upon successful completion, these functions return OK. Otherwise, they return ERR. ERRORS
No errors are defined. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |Unsafe | +-----------------------------+-----------------------------+ SEE ALSO
getch(3XCURSES), getstr(3XCURSES), initscr(3XCURSES), libcurses(3XCURSES), scanw(3XCURSES), attributes(5), standards(5) SunOS 5.11 5 Jun 2002 echo(3XCURSES)
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