addpath

# Hey EMACS, this should be in -*- sh -*- mode
#
# Routines to modify environment variables.
# This is sourced from my .bashrc file.
#
# Author: Eric Engstrom (engstrom@mtu.net)
##

# Add to the path variable named by $1 the component $2. 
# $3 must be "append" or "prepend" to indicate where the component is added.
# $4 optionally specifies the separator character... 
# separator defaults to ":" or ";" if the latter is already used.
addpath () {
    local p s v r
    if [ -z "$2" -o ! -e "$2" ]; then return; fi
    p=$1
    v=${!p}
    test "$v" != "${v%%;*}" && s=';'
    s=${s:-":"}
    s=${4:-"$s"}
    case "$v" in
	*"$s$2$s"*|*"$s$2"|"$2$s"*|"$2")	r="$v";;
	"")					r="$2";;
	*)			case "$3" in
					p*)	r="$2$s$v";;
					a*)	r="$v$s$2";;
				esac
    esac
    export $p="$r"
}

# convenience routines which append/prepend a string to a path.
append () { addpath "$1" "$2" append "$3"; }
prepend () { addpath "$1" "$2" prepend "$3"; }

# Substitute $3 for $2 at the end of all components of path variable
# named by $1 and return the subset which represent existing directories
#p=$PATH; until [ $p = $d ]; do d=${p%%:*}; m=${d/%bin/man}; ; p=${p#*:}; done
substpath() {
    local p d m r a b
    p=${!1}
    a=$2
    b=$3
    until [ "$p" == "$d" ]; do
        d=${p%%:*}
        m=${d/%$a/$b};
        if [ "$d" != "$m" -a -d "$m" ]; then
            r=$r:$m
        fi
        p=${p#*:}
    done 
    echo ${r#:}
}

# Replace all substrings of $2 with $3 in the variable named by $1
replpath () {
    local p v r
    if [ -z "$3" -o ! -e "$3" ]; then return; fi
    p=$1
    v=${!p}
    r=${v//$2/$3}
    #echo "$p - $v - $r"
    export $p="$r"
    hash -r
}

# Remove all path components $2 from the variable named by $1
rmpath () {
    local p v r
    if [ -z "$2" ]; then return; fi
    p=$1
    v=${!p}
    r=${v//$2}
    r=${r//::/:}  # remove doubled path separators
    echo "$p - $v - $r"
    export $p="$r"
    hash -r
}

# Use a "New" version for a package by updating the corresponding
# ${PACKAGE}DIR variable as well as the PATH and MANPATH variables.
# NOTE: HIGHLY dependent upon my conventions for Package directory
# variables as well as PATH and MANPATH conventions
newpkg() {
    local d v r
    # check parameters
    if [ "$#" -ne 2 ]; then 
        echo "Usage: $FUNCNAME <pkg> <ver>"
        return 
    fi
    # compute the package-dir variable name
    d=`echo "$1DIR" | tr a-z A-Z`
    if [ -z "${!d}" ]; then
        echo "$FUNCNAME(): no package-dir variable named '${d}'" 1>&2
        return
    fi
    # compute the new value of the pkg-dir
    v=${!d}
    r="${v%/*}/$2"
    if [ ! -d "$r" ]; then
        echo "$FUNCNAME(): no package directory named '${r}'" 1>&2
        return
    fi
    # set the value of the package variable to the new value
    replpath PATH "$v" "$r"
    replpath MANPATH "$v" "$r"
    export $d="$r"
    echo "${d} is now '${!d}'; in \$PATH and \$MANPATH"
}

# eof .addpath