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Top Forums Shell Programming and Scripting Syntax error piping to bc on command line - works when assigned to var Post 302588604 by gencon on Monday 9th of January 2012 12:16:03 PM
Old 01-09-2012
Syntax error piping to bc on command line - works when assigned to var

I have a script which outputs some timing data a line at a time. There are approx. 10 lines echoed, each line looks something like this:
Code:
0.741 http://checkip.dyndns.org 94.170.119.226

Since I needed to add all the values in the first column, I piped the output to grep, matching and printing the first numerical column, then piped it on to tr to replace new lines with '+', then piped to sed to replace the final '+' with nothing, and finally to bc to add the values. Then bc gave me a stdin syntax error - damn it, maybe I'm not quite so clever as I thought I was. Smilie

On examining the code I discovered that if I left off the final pipe to bc I got what I thought I should have - that being:
Code:
$ getip test | grep -o "^[0-9.]*" | tr "\n\r\f" "+" | sed "s/\(.*\)+/\1/" 
0.409+0.087+0.116+0.294+0.214+0.342+0.595+0.232+0.380+0.494 [Note: no new line, prompt is here as expected]

$ echo 0.409+0.087+0.116+0.294+0.214+0.342+0.595+0.232+0.380+0.494 | bc
3.163

So I copied and pasted those values into an echo statement, piped to bc, and it worked fine as shown above.

As another test I ran the command again, this time assigning the result to a variable, and then piped the variable to bc. That also worked fine, see code below (the top line has the error shown when piped to bc):
Code:
$ getip test | grep -o "^[0-9.]*" | tr "\n\r\f" "+" | sed "s/\(.*\)+/\1/" | bc
(standard_in) 1: syntax error

$ var1=$(getip test | grep -o "^[0-9.]*" | tr "\n\r\f" "+" | sed "s/\(.*\)+/\1/")

$ echo $var1
0.332+0.111+0.081+0.283+0.155+0.355+0.607+0.297+0.382+0.452+0.294

$ echo $var1 | bc
3.349

What I want to know is why I get the syntax error from bc when I run it as one line? Any ideas?

Many thanks.

PS. The somewhat simpler alternative works with no problems.
Code:
$ getip test | grep -o "^[0-9.]*" | awk '{sum+=$1} END {print sum}'
2.999

 

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scroll(3NCURSES)														  scroll(3NCURSES)

NAME
scroll, scrl, wscrl - scroll a curses window SYNOPSIS
#include <curses.h> int scroll(WINDOW *win); int scrl(int n); int wscrl(WINDOW *win, int n); DESCRIPTION
The scroll routine scrolls the window up one line. This involves moving the lines in the window data structure. As an optimization, if the scrolling region of the window is the entire screen, the physical screen may be scrolled at the same time. For positive n, the scrl and wscrl routines scroll the window up n lines (line i+n becomes i); otherwise scroll the window down n lines. This involves moving the lines in the window character image structure. The current cursor position is not changed. For these functions to work, scrolling must be enabled via scrollok. RETURN VALUE
These routines return ERR upon failure, and OK (SVr4 only specifies "an integer value other than ERR") upon successful completion. X/Open defines no error conditions. This implementation returns an error if the window pointer is null, or if scrolling is not enabled in the window, e.g., with scrollok. NOTES
Note that scrl and scroll may be macros. The SVr4 documentation says that the optimization of physically scrolling immediately if the scroll region is the entire screen "is" per- formed, not "may be" performed. This implementation deliberately does not guarantee that this will occur, to leave open the possibility of smarter optimization of multiple scroll actions on the next update. Neither the SVr4 nor the XSI documentation specify whether the current attribute or current color-pair of blanks generated by the scroll function is zeroed. Under this implementation it is. PORTABILITY
The XSI Curses standard, Issue 4 describes these functions. SEE ALSO
ncurses(3NCURSES), outopts(3NCURSES) scroll(3NCURSES)
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