source: vendor/bash/3.1-p17/examples/scripts.v2/vtree

#! /bin/bash
#
# original from:
# vtree: visual directory tree
# @(#) vtree.sh 1.1 91/07/01
# 90/04 john h. dubois iii (john@armory.com)
# 91/07/01 fixed bug that caused problems when dir given on command line,
#          added some info to help, changed to 4-space indenting
#
# conversion to bash v2 syntax done by Chet Ramey
#
help=\
"Syntax: vtree [startdir] [namelen=#] [linelen=#]
If startdir is not specified, tree will start at current dir.

namelen specifies the minimum number of characters of a directory name that
are guaranteed to be printed.
This is a tradeoff between the number of tree levels that can fit on a
screen line and the number of chars of each dir name that can be printed.
In most cases it will be possible to print more than namelen characters of
the name (a name up to namelen+1 chars will always be printed in full),
but in some cases truncation down to namelen chars will occur.
If truncation occurs, a '>' is printed at the end of the name.
namelen=8 (the default) typically causes about 5 dirs/1000 to be truncated.
namelen=7 typically causes about 10 dirs/1000 to be truncated.
namelen=8 will allow 6 full length dirs to be printed in 79 columns.
namelen=7 will allow 7 full length dirs to be printed in 79 columns;

linelen specifies the maximum number of characters to print on one screen
line.  All characters beyond this are truncated.  The default is 1024.
To avoid line wrap on an 80 column terminal with autowrap, use linelen=79.
"

for i in "$@"; do
    case $i in
    -h) echo "$help"; exit;;
    *=*)
        vars="$vars $i"
        ;;
    *)
        if [ ! -x $i ] || [ ! -d $i ]; then     # arg must be a dir and executable
            echo "$i: directory not accessible."
            exit
        fi
        cd $i
        ;;
    esac
    shift
done

pwd     # print path of root of tree

# find all directories depth first; ignore permission errors
find . -type d -print 2> /dev/null | \
gawk -F/ '

# Do this block for NR == 1 instead of BEGIN because command line var
# assignments are not done until after BEGIN block is executed.
NR == 1 {
    if (namelen)
        MaxLen = namelen;
    else
        MaxLen = 8;
    if (!linelen)
        linelen = 1024
    HSpace = substr("              ",1,MaxLen);     # used to indent tree
    n = 0;          # number of dirs found on one major branch
}

$0 != "." {     # do for every line produced by find except tree root dir
    if (NF == 2 && n > 0)   # print major branch whenever a new one starts
        list();
    Depth[n] = NF - 1;      # record depth and name of dir
     Name[n++] = $NF;
}

END {
    list()  # print last major branch
}

function list() {
    Line = Name[0];     # initialize first line of branch to be branch base
    for (i = 1; i < n; i++) {   # for each name in major branch
        if (Depth[i] == Depth[i-1] + 1)
            AddHLink(); # if moving deeper into branch, use same line
        else {
            print substr(Line,1,linelen);   # last line is done; print it
            Line = "";  # start new line
            # print indentation, vert links, and vert/horiz links
            for (d = 1; d < Depth[i] - 1; d++)  # for each level of indentation
                # if a vert. link has been established for this level
                if (VLink[d])
                    Line = Line HSpace " |  ";
                else        # print empty indentation
                    Line = Line HSpace "    ";
            # Print last part of vert. link
            if (VLink[d] == i) {
                VLink[d] = 0;   # mark level for no vert link
                Line = Line HSpace " \\--";
            }
            else
                Line = Line HSpace " |--";
        }
        Line = Line Name[i];    # Add dir name to line
    }
    print substr(Line,1,linelen);   # print last line of major branch
    n = 0;      # reset name counter
}

function AddHLink() {
    NDepth = Depth[i];  # Depth of this name
    VLink[NDepth - 1] = 0;
    # search until a name found at a level less than this one
    for (j = i + 1; j < n && Depth[j] >= NDepth; j++)
        # keep track of last name that VLink should connect to
        if (Depth[j] == NDepth)
            VLink[NDepth - 1] = j;
    if (VLink[NDepth - 1]) {
        NLine = substr(Line,1,(NDepth - 2) * (MaxLen + 4) + MaxLen + 1);
        if (length(NLine) < length(Line))
            Line = substr(NLine,1,length(NLine) - 1) ">"
        else
            Line = NLine;
        Line = Line substr("--------------+--",
            18 - ((NDepth - 1) * (MaxLen + 4) - length(Line)));
    }
    else {
        NLine = substr(Line,1,(NDepth - 2) * (MaxLen + 4) + MaxLen + 3);
        if (length(NLine) < length(Line))
            Line = substr(NLine,1,length(NLine) - 1) ">"
        else
            Line = NLine;
        Line = Line substr("-----------------",
            1,(NDepth - 1) * (MaxLen + 4) - length(Line));
    }
}
' $vars