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Created by Dr. Xi on December 05, 2009 20:12:16    Last update: December 05, 2009 20:46:45
It's quite easy for Perl to open a pipe and read from it: $file = "nospace.txt"; open(IN, "cat $file |") ... But the code breaks when the file name contains a space: # This does not work! $file = "yes space.txt"; ... On Windows, these don't work either: # This does not work! $file = "yes space.txt"; ... You need to use a technique called Safe Pipe Opens : $file = "yes space.txt"; $prog = "cat"; ...
Created by Dr. Xi on September 29, 2008 23:03:40    Last update: September 29, 2008 23:04:08
Variables set automatically by shell: Variable Description $# Number of command-line arguments. $- Options currently in effect (arguments supplied to sh or to set). $? Exit value of last executed command. $$ Process number of current process. $! Process number of last background command. $0 First word; that is, command name. $n Individual arguments on command line (positional parameters). The Bourne shell allows only nine parameters to be referenced directly (n = 1-9); the Korn shell allows n to be greater than 9 if specified as ${n}. $* All arguments on command line ("$1 $2..."). $@ All arguments on command line, individually quoted ("$1" "$2" ...). Variables set automatically by Korn shell: Variable Description ERRNO Error number of last system call that failed. LINENO Current...
Created by Dr. Xi on September 23, 2008 20:43:58    Last update: September 23, 2008 20:43:58
Variable Description $0 The name of the ruby script file $* The command line arguments $$ Ruby interpreter's process ID $? Exit status of last executed child process $_ String last read by gets $. Line number last read by interpreter $! Last error message $@ Location of error $& String last matched by regexp $~ The last regexp match, as an array of subexpressions $n the nth subexpression in the last match (same as $~ ) $= Sase-insensitivity flag $/ Input record separator $\ Output record separator