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Top Forums Shell Programming and Scripting awk evaluating a string as a math expression Post 302841151 by avi.levi on Wednesday 7th of August 2013 04:44:22 AM
Old 08-07-2013
awk evaluating a string as a math expression

Hi,
I am writing a script in awk trying to replace strings that are math expressions with their result.
For example, I have a file that looks like this:

5-1
32/8-1
4*12
17+1-3

I would like to get the following output:

4
3
48
15

I tried doing it the following way (using the "bc" unix command):
Get the string into an awk variable and then send it to the shell.

The following line works (without using an input variable).
The outputVariable gets the correct answer "4".
Code:
"echo 5-1 | bc" | getline outputVariable;

So, I tried doing it like this:
Code:
"echo "inputVariable" | bc" | getline outputVariable;

This, of course, does not work.

I tried printing it to a file and then taking the string from a file:
Code:
print inputVariable > "./temp"
"tail -1 ./temp | bc" | getline outputVar

This does not work either.

I am out of ideas.

P.S
I did not come up with any way to transform the string into a math expression that awk can process internally (without going to shell).
Maybe there's a way, and this can be a good solution for me.

Thank you for your help.
 

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IRSEND(1)								FSF								 IRSEND(1)

NAME
irsend - basic LIRC program to send infra-red commands SYNOPSIS
irsend [options] DIRECTIVE REMOTE CODE [CODE...] DESCRIPTION
Asks the lircd daemon to send one or more CIR (Consumer Infra-Red) commands. This is intended for remote control of electronic devices such as TV boxes, HiFi sets, etc. DIRECTIVE can be: SEND_ONCE - send CODE [CODE ...] once SEND_START - start repeating CODE SEND_STOP - stop repeating CODE LIST - list configured remote items SET_TRANSMITTERS - set transmitters NUM [NUM ...] SIMULATE - simulate IR event REMOTE is the name of a remote, as described in the lircd configuration file. CODE is the name of a remote control key of REMOTE, as it appears in the lircd configuration file. NUM is the transmitter number of the hardware device. For the LIST DIRECTIVE, REMOTE and/or CODE can be empty: LIST "" "" - list all configured remote names LIST REMOTE "" - list all codes of REMOTE LIST REMOTE CODE - list only CODE of REMOTE The SIMULATE command only works if it has been explicitly enabled in lircd. -h --help display usage summary -v --version display version -d --device use given lircd socket [/var/run/lirc/lircd] -a --address=host[:port] connect to lircd at this address -# --count=n send command n times EXAMPLES
irsend LIST DenonTuner "" irsend SEND_ONCE DenonTuner PROG-SCAN irsend SEND_ONCE OnkyoAmpli VOL-UP VOL-UP VOL-UP VOL-UP irsend SEND_START OnkyoAmpli VOL-DOWN ; sleep 3 irsend SEND_STOP OnkyoAmpli VOL-DOWN irsend SET_TRANSMITTERS 1 irsend SET_TRANSMITTERS 1 3 4 irsend SIMULATE "0000000000000476 00 OK TECHNISAT_ST3004S" FILES
/etc/lirc/lircd.conf Default lircd configuration file. It should contain all the remotes, their infra-red codes and the corresponding timing and wave- form details. DIAGNOSTICS
If lircd is not running (or /var/run/lirc/lircd lacks write permissions) irsend aborts with the following diagnostics: "irsend: could not connect to socket" "irsend: Connection refused" (or "Permission denied"). SEE ALSO
The documentation for lirc is maintained as html pages. They are located under html/ in the documentation directory. lircd(8), mode2(1), smode2(1), xmode2(1), irrecord(1), irw(1), http://www.lirc.org. irsend 0.8.7pre1 May 2010 IRSEND(1)
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