07-27-2009
Trying a arithmatic on a command line vs scripting.
Hi Everyone!
I'm trying to do simple math on a single command line instead of a script which I've already set up using let etc. I can not get the same output to display on a command line.
Essentially I would like a=20, b=50, and c=a*b.
When I tried:
let "A=20, B=50"; let C=A*B; echo $C
I got the answer but the following error message:
-bash: let: 1000=A*B; attempted assignment to non-varible (error token is "=A*B")
I didn't know if that meant to add quotes in the formula...so i tried that and it didn't work either. Where am i making the mistake?
Thanks so much!
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DDB(8) BSD System Manager's Manual DDB(8)
NAME
ddb -- configure DDB kernel debugger properties
SYNOPSIS
ddb capture [-M -core] [-N -system] print
ddb capture [-M -core] [-N -system] status
ddb script scriptname
ddb script scriptname=script
ddb scripts
ddb unscript scriptname
ddb pathname
DESCRIPTION
The ddb utility configures certain aspects of the ddb(4) kernel debugger from user space that are not configured at compile-time or easily
via sysctl(8) MIB entries.
To ease configuration, commands can be put in a file which is processed using ddb as shown in the last synopsis line. An absolute pathname
must be used. The file will be read line by line and applied as arguments to the ddb utility. Whitespace at the beginning of lines will be
ignored as will lines where the first non-whitespace character is '#'.
OUTPUT CAPTURE
The ddb utility can be used to extract the contents of the ddb(4) output capture buffer of the current live kernel, or from the crash dump of
a kernel on disk. The following debugger commands are available from the command line:
capture [-M core] [-N system] print
Print the current contents of the ddb(4) output capture buffer.
capture [-M core] [-N system] status
Print the current status of the ddb(4) output capture buffer.
SCRIPTING
The ddb utility can be used to configure aspects of ddb(4) scripting from user space; scripting support is described in more detail in
ddb(4). Each of the debugger commands is available from the command line:
script scriptname
Print the script named scriptname.
script scriptname=script
Define a script named scriptname. As many scripts contain characters interpreted in special ways by the shell, it is advisable to
enclose script in quotes.
scripts
List currently defined scripts.
unscript scriptname
Delete the script named scriptname.
EXIT STATUS
The ddb utility exits 0 on success, and >0 if an error occurs.
EXAMPLES
The following example defines a script that will execute when the kernel debugger is entered as a result of a break signal:
ddb script kdb.enter.break="show pcpu; bt"
The following example will delete the script:
ddb unscript kdb.enter.break
For further examples, see the ddb(4) and textdump(4) manual pages.
SEE ALSO
ddb(4), textdump(4), sysctl(8)
HISTORY
The ddb utility first appeared in FreeBSD 7.1.
AUTHORS
Robert N M Watson
BUGS
Ideally, ddb would not exist, as all pertinent aspects of ddb(4) could be configured directly via sysctl(8).
BSD
December 24, 2008 BSD