05-16-2007
If the course says that ((~ 2#1001)) evaluates to 2#110, I wonder what shell they were using. With ksh I get:
$ typeset -i2 b
$ echo $((2#1001)) $((b=~2#1001)) $b
9 -10 -2#1010
With bash, there is no -i2 and I don't see an easy way to get binary output. I could code my own routine, but then the behavior would be whatever I decided. (But I get the "9 -10" part with bash.) Since ksh alone has a way to output binary, I did a few experiments with it. A negative number has many leading 1's while a non-negative has many leading zeros. ksh uses enough positions to output the the leftmost bit transistion. If you exceed the shell's integer size, you get undefined results, but clamping at positive or negative "infinity" (max/min integer) is common with both ksh and bash. The shells I checked have either 32 or 64 bit integers.
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LEARN ABOUT DEBIAN
surfraw-update-path
SURFRAW-UPDATE-PATH(1) User Contributed Perl Documentation SURFRAW-UPDATE-PATH(1)
NAME
surfraw-update-path - updates PATH in shell config files
SYNOPSIS
surfraw-update-path [-add] [-remove] [-check] [-sys] [-all] [-help] [-shell=SHELL]
DESCRIPTION
surfraw-update-path adds the surfraw elvi directory (/usr/lib/surfraw) to your PATH in your shell's config file.
Currently it supports bash, sh, csh, tcsh, ash, dash, ksh, pdksh, zsh, rc, and es
Don't forget to login again or source your login files for it to take effect.
OPTIONS
-check
Checks to see if the surfraw config code is present. This is the default.
-add
Adds the surfraw config code.
-remove
Removes the surfraw config code
-sys
Updates the system-wide shell config instead of the user. Must be done as root.
-shell=SHELL
Selects the shell to configure. Defaults to the value of the $SHELL environment variable.
Currently supported shells are:
sh, ash, bash, dash, csh, tcsh, ksh, pdksh, zsh, rc, and es.
-all
Attempts to configure the startup files for all known shells
-help
Gives a usage message
RETURN VALUE
-check returns 0 if the surfraw code is present in the file, 1 if it is not found, or 2 on error.
All other options return 0 on success, or 2 on error.
ENVIRONMENT
SHELL
Used to determine which shell to configure, if -shell is not given.
HOME
Used to find users config files.
ENV Used by posix-compliant shells to specify a startup rc file.
ZDOTDIR
Used to find user config files for zsh. If not set, defaults to HOME.
SEE ALSO
surfraw(1), sh(1), ash(1), bash(1), dash(1), csh(1), tcsh(1), ksh(1), pdksh(1), zsh(1), rc(1), es(1)
AUTHOR
Ian Beckwith <ianb@erislabs.net>
perl v5.12.4 2011-07-12 SURFRAW-UPDATE-PATH(1)