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Differences in Variable Scope in Shell Functions

Ksh93 and bash have subtly different scopes for variables defined in shell functions as the following example shows: # POSIX function syntax testme2() { printf “Function testme2 invokedn” var21=testme21 typeset var22=testme22 } function testme1 { printf “Function testme1 invokedn” var11=testme11 typeset var12=testme12 } testme1 echo “VAR11=$var11” echo “VAR12=$var12” Here is the output when run under ksh93: Function testme1 invoked VAR11=testme11 VAR12= Function testme2 invoked VAR21=testme21 VAR22=testme22 and here is the output when run under bash: Function testme1 invoked VAR11=testme11 VAR12= Function testme2 invoked VAR21=testme21 VAR22= Note the different output for var22! Ksh93 has lexical scoping. A variable is normally global

Accessing Cisco Secure ACS 5.X Internals

Cisco Secure Access Control System is based on CentOS. This post will show you how to access the Bash shell as root, and explores the underlying filesystem layout and utilities which make up this product..

Fedora 18 Supports 256 Color Terminals

You may not be aware of it but currently Linux terminal emulators such as xterm only supports 8 colors while those on Apple’s OS X support 256 colors. Now, beginning with Fedora 18, Fedora will also support 256 colors via the xterm-256color terminfo database entry. To see how many colors a terminal supports: $ echo $TERM xterm-256color $ tput colors 256 I have never liked the default colors produced by the –color color option to ls and other utilities and, as a result, have normally removed such aliases from my bash startup scripts. Having 32 times more colors available gives

Implementing strstr in Korn Shell

Neither Bash or the Korn Shell 93 (ksh93) provide a C-like strstr builtin. Here is a simple implementation of a strstr function in ksh93. The strstr function finds the first occurrence of s2 in s1. If s2 is an empty string, 0 is returned; if s2 occurs nowhere in s1, 0 is also returned; otherwise the offset to the first character of the first occurrence of s2 is returned. #!/bin/ksh function strstr { typeset s1=”$1″ typeset s2=”$2″ if [[ ${#s2} == 0 ]] then return 0 fi typeset len=${#s1} typeset first=${s1%%${s2}*}x typeset ndx=${#first} if (( ndx > len )) then

Bash Hash Builtin

The Bash shell hash builtin maintains a hash cache (table) containing the full pathname of previously executed commands that are on your PATH environmental variable. If the command is in the hash table, it just executes it without searching for it in the various path components. SYNTAX hash [-r] [-p filename] [name] OPTIONS -r Reset (causes the shell to forget all remembered locations) -p Use filename as the location of name (don’t search $PATH) If no arguments are given, information about remembered commands is printed. The return status is zero unless a name is not found or an invalid option