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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

First Letter Capitalization in Bash and Korn Shell

Bash does not have a built-in facility to first letter capitalize a string but Bash 4.0 and later has the necessary tools to do so as shown by the following example: #!/bin/bash Firstcap() { lower=${1,,} echo ${lower^} } Firstcap lINUX >>> OUTPUT IS: Linux This function not only uppercases the first letter of the argument passed to it but also lowercases the remaining letters of the argument. Here is how to do the same thing in ksh93: #!/bin/ksh Firstcap() { typeset -u f f=${1:0:1} typeset -l r r=${1:1} echo “${f}${r}” } Firstcap lINUX >>> OUTPUT IS: Linux

Bash and Korn Shell Let Keyword

Recently a colleague of mine recommended using the let keyword in shell scripts to perform arithmetic evaluation. That prompted me to write this post about the let keyword. Here is what the bash manpage says about the let keyword: let arg [arg …] Each arg is an arithmetic expression to be evaluated. If the last arg evaluates to 0, let returns 1; 0 is returned otherwise. And here is a simple example of it’s use: $ a=2 $ b=5 $ let c=$a+$b $ echo $c 7 $ let c=$a + $b $ echo $c 2 As you can see from