mirror of https://github.com/tLDP/LDP
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gferg
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/*********************************************/
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/* ascii.c */
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/* Generate ASCII table */
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/* To build: gcc -O2 ascii.c -o ascii-table */
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/* */
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/* This utterly trivial program written by */
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/* Mendel Cooper, 04/07 */
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/* I'm not proud of it, but it does the job. */
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/* License: Public Domain */
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/*********************************************/
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#include <stdio.h>
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#define MAX 255 /* FF hex */
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#define FILENAME "ASCII.txt" /* Outfile name */
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int main()
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{
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int i;
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FILE *fp;
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fp = fopen (FILENAME, "a" );
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for( i = 1; i <= MAX; i++ ) {
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fprintf( fp, "%5d ", i );
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fputc( i, fp );
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fprintf( fp, " " );
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if ( i % 5 == 0 )
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fprintf( fp, "\n" );
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}
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fprintf( fp, "\n" );
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return (0);
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} /* Outfile needs a bit of hand-editing for tidying up. */
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/* Try rewriting this as a shell script. */
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/* Not so easy, huh? */
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@ -0,0 +1,115 @@
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#!/bin/bash
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# brownian.sh
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# Author: Mendel Cooper
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# Reldate: 10/26/07
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# License: GPL3
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# ----------------------------------------------------------------
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# This script models Brownian motion:
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#+ the random wanderings of tiny particles in a fluid,
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#+ as they are impacted by random currents and collisions.
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#+ This is also known as the "Drunkard's Walk."
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# It can also be considered as a highly simplified simulation of a
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#+ Galton Board, a slanted board with a pattern of pegs,
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#+ down which rolls a succession of marbles, one at a time.
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#+ At the bottom is a row of slots or catch basins in which
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#+ the marbles finally come to rest.
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# Think of it as a kind of bare-bones Pachinko game.
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# As you see by running the script,
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#+ most of the marbles cluster around the center slot.
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#+ This mirrors the expected "Normal Distribution."
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# As a Galton Board simulation, this script
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#+ disregards such parameters as
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#+ board tilt-angle, rolling friction of the marbles,
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#+ angles of impact, and elasticity of the pegs.
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# How much of a difference does that make?
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# ----------------------------------------------------------------
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PASSES=500 # Number of particle interactions / marbles.
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ROWS=10 # Number of "collisions" (or horizontal peg rows).
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RANGE=3 # We want 0 - 2 output range from $RANDOM.
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POS=0 # Left/right position.
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declare -a Slots # Array holding cumulative results of passes.
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NUMSLOTS=21 # How many slots at bottom of board?
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Initialize_Slots () { # Zero out all elements of array.
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for i in $( seq $NUMSLOTS )
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do
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Slots[$i]=0
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done
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echo # Blank line at beginning of run.
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}
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Show_Slots () {
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echo -n " "
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for i in $( seq $NUMSLOTS ) # Pretty-print array elements.
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do
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printf "%3d" ${Slots[$i]} # Three spaces per result.
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done
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echo # Row of slots:
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echo " |__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|"
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echo " ^^"
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echo # Note that if the count within any particular slot exceeds 99,
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#+ it messes up the display.
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# Running only(!) 500 passes usually avoids this.
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}
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Move () { # Move one unit right / left, or stay put.
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Move=$RANDOM # How random is $RANDOM? Let's see. ...
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let "Move %= RANGE" # Normalize into range of 0 - 2.
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case "$Move" in
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0 ) ;; # Do nothing, i.e., stay in place.
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1 ) ((POS--));; # Left.
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2 ) ((POS++));; # Right.
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* ) echo -n "Error ";; # Should never happen.
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esac
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}
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Play () { # Single pass (inner loop).
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i=0
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while [ $i -lt $ROWS ] # One event per row.
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do
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Move
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((i++));
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done
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SHIFT=11 # Why 11, and not 10?
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let "POS += $SHIFT" # Shift "zero position" to center.
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(( Slots[$POS]++ )) # DEBUG: echo $POS
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}
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Run () { # Outer loop.
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p=0
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while [ $p -lt $PASSES ]
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do
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Play
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(( p++ ))
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POS=0 # Reset to zero. Why?
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done
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}
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# --------------
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# main ()
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Initialize_Slots
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Run
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Show_Slots
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# --------------
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exit $?
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# Exercises:
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# ---------
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# 1) Show the results in a vertical bar graph, or as an alternative,
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#+ a scattergram.
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# 2) Alter the script to use /dev/urandom instead of $RANDOM.
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# Does this make the results more random?
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@ -0,0 +1,36 @@
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#!/bin/bash
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# Optimized Sieve of Eratosthenes
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# Script by Jared Martin, with very minor changes by ABS Guide author.
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# Used in ABS Guide with permission (thanks!).
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# Based on script in Advanced Bash Scripting Guide.
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# http://tldp.org/LDP/abs/html/arrays.html#PRIMES0 (ex68.sh).
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# http://www.cs.hmc.edu/~oneill/papers/Sieve-JFP.pdf (reference)
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# Check results against http://primes.utm.edu/lists/small/1000.txt
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# Necessary but not sufficient would be, e.g.,
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# (($(sieve 7919 | wc -w) == 1000)) && echo "7919 is the 1000th prime"
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UPPER_LIMIT=${1:?"Need an upper limit of primes to search."}
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Primes=( '' $(seq ${UPPER_LIMIT}) )
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typeset -i i t
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Primes[i=1]='' # 1 is not a prime.
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until (( ( i += 1 ) > (${UPPER_LIMIT}/i) )) # Need check only ith-way.
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do # Why?
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if ((${Primes[t=i*(i-1), i]}))
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# Obscure, but instructive, use of numeric eval in subscript.
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then
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until (( ( t += i ) > ${UPPER_LIMIT} ))
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do Primes[t]=; done
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fi
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done
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# echo ${Primes[*]}
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echo # Change to original script for pretty-printing (80-col. display).
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printf "%8d" ${Primes[*]}
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echo; echo
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exit $?
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@ -0,0 +1,24 @@
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#!/bin/bash
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# from.sh
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# Emulates the useful "from" utility in Solaris, BSD, etc.
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# Echoes the "From" header line in all messages
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#+ in your e-mail directory.
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MAILDIR=~/mail/* # No quoting of variable. Why?
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GREP_OPTS="-H -A 5 --color" # Show file, plus extra context lines
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#+ and display "From" in color.
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TARGETSTR="^From" # "From" at beginning of line.
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for file in $MAILDIR # No quoting of variable.
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do
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grep $GREP_OPTS "$TARGETSTR" "$file"
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# ^^^^^^^^^^ # Again, do not quote this variable.
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echo
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done
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exit $?
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# Might wish to pipe the output of this script to 'more' or
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#+ redirect it to a file . . .
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#!/bin/bash
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# insertion-sort.bash: Insertion sort implementation in Bash
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# Heavy use of Bash array features:
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#+ (string) slicing, merging, etc
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# URL: http://www.lugmen.org.ar/~jjo/jjotip/insertion-sort.bash.d
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#+ /insertion-sort.bash.sh
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#
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# Author: JuanJo Ciarlante <jjo@irrigacion.gov.ar>
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# Lightly reformatted by ABS Guide author.
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# License: GPLv2
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# Used in ABS Guide with author's permission (thanks!).
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#
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# Test with: ./insertion-sort.bash -t
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# Or: bash insertion-sort.bash -t
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# The following *doesn't* work:
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# sh insertion-sort.bash -t
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# Why not? Hint: which Bash-specific features are disabled
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#+ when running a script by 'sh script.sh'?
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#
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: ${DEBUG:=0} # Debug, override with: DEBUG=1 ./scriptname . . .
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# Parameter substitution -- set DEBUG to 0 if not previously set.
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# Global array: "list"
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typeset -a list
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# Load whitespace-separated numbers from stdin.
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if [ "$1" = "-t" ]; then
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DEBUG=1
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read -a list < <( od -Ad -w24 -t u2 /dev/urandom ) # Random list.
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# ^ ^ process substition
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else
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read -a list
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fi
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numelem=${#list[*]}
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# Shows the list, marking the element whose index is $1
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#+ by surrounding it with the two chars passed as $2.
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# Whole line prefixed with $3.
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showlist()
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{
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echo "$3"${list[@]:0:$1} ${2:0:1}${list[$1]}${2:1:1} ${list[@]:$1+1};
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}
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# Loop _pivot_ -- from second element to end of list.
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for(( i=1; i<numelem; i++ )) do
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((DEBUG))&&showlist i "[]" " "
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# From current _pivot_, back to first element.
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for(( j=i; j; j-- )) do
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# Search for the 1st elem. less than current "pivot" . . .
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[[ "${list[j-1]}" -le "${list[i]}" ]] && break
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done
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(( i==j )) && continue ## No insertion was needed for this element.
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# . . . Move list[i] (pivot) to the left of list[j]:
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list=(${list[@]:0:j} ${list[i]} ${list[j]}\
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# {0,j-1} {i} {j}
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${list[@]:j+1:i-(j+1)} ${list[@]:i+1})
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# {j+1,i-1} {i+1,last}
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((DEBUG))&&showlist j "<>" "*"
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done
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|
||||
|
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echo
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echo "------"
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echo $'Result:\n'${list[@]}
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exit $?
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@ -0,0 +1,177 @@
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<table>
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<title>Operator Precedence</title>
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<tgroup cols="3">
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<thead>
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||||
<row>
|
||||
<entry>Operator</entry>
|
||||
<entry>Meaning</entry>
|
||||
<entry>Comments</entry>
|
||||
</row>
|
||||
</thead>
|
||||
<tbody>
|
||||
<row>
|
||||
<entry><option></option></entry>
|
||||
<entry></entry>
|
||||
<entry><command>HIGHEST PRECEDENCE</command></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>var++ var--</option></entry>
|
||||
<entry>post-increment, post-decrement</entry>
|
||||
<entry><link linkend="cstyle">C-style</link> operators</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>++var --var</option></entry>
|
||||
<entry>pre-increment, pre-decrement</entry>
|
||||
<entry></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>! ~</option></entry>
|
||||
<entry><link linkend="notref">negation</link></entry>
|
||||
<entry>logical / bitwise, inverts sense of following
|
||||
operator</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>**</option></entry>
|
||||
<entry><link
|
||||
linkend="exponentiationref">exponentiation</link></entry>
|
||||
<entry><link linkend="arops1">arithmetic
|
||||
operation</link></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>* / %</option></entry>
|
||||
<entry>multiplication, division, modulo</entry>
|
||||
<entry>arithmetic operation</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>+ -</option></entry>
|
||||
<entry>addition, subtraction</entry>
|
||||
<entry>arithmetic operation</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option><< >></option></entry>
|
||||
<entry>left, right shift</entry>
|
||||
<entry><link linkend="bitwsops1">bitwise</link></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>-z -n</option></entry>
|
||||
<entry><firstterm>unary</firstterm> comparison</entry>
|
||||
<entry>string is/is-not <firstterm>null</firstterm></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>-e -f -t -x, etc.</option></entry>
|
||||
<entry><firstterm>unary</firstterm> comparison</entry>
|
||||
<entry><firstterm>files</firstterm></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>< -lt > -gt <= -le >= -ge</option></entry>
|
||||
<entry><firstterm>compound</firstterm> comparison</entry>
|
||||
<entry>string and integer</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>-nt -ot -ef</option></entry>
|
||||
<entry><firstterm>compound</firstterm> comparison</entry>
|
||||
<entry><firstterm>files</firstterm></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>== -eq != -ne</option></entry>
|
||||
<entry>equality / inequality</entry>
|
||||
<entry>test operators, string and integer</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>&</option></entry>
|
||||
<entry>AND</entry>
|
||||
<entry>bitwise</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>^</option></entry>
|
||||
<entry>XOR</entry>
|
||||
<entry><firstterm>exclusive</firstterm> OR, bitwise</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>|</option></entry>
|
||||
<entry>OR</entry>
|
||||
<entry>bitwise</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>&& -a</option></entry>
|
||||
<entry>AND</entry>
|
||||
<entry>logical, <firstterm>compound</firstterm>
|
||||
comparison</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>|| -o</option></entry>
|
||||
<entry>OR</entry>
|
||||
<entry>logical, <firstterm>compound</firstterm>
|
||||
comparison</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>?:</option></entry>
|
||||
<entry><link linkend="cstrinary">trinary
|
||||
operator</link></entry>
|
||||
<entry>C-style</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>=</option></entry>
|
||||
<entry><link linkend="eqref">assignment</link></entry>
|
||||
<entry>(do not confuse with equality
|
||||
<firstterm>test</firstterm>)</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>*= /= %= += -= <<= >>= &= !=</option></entry>
|
||||
<entry><link linkend="arithopscomb">combination
|
||||
assignment</link></entry>
|
||||
<entry>times-equal, divide-equal, mod-equal, etc.</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
<entry></entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option>,</option></entry>
|
||||
<entry><link linkend="commaop">comma</link></entry>
|
||||
<entry>links a sequence of operations</entry>
|
||||
</row>
|
||||
<row>
|
||||
<entry><option></option></entry>
|
||||
<entry></entry>
|
||||
<entry><command>LOWEST PRECEDENCE</command></entry>
|
||||
</row>
|
||||
</tbody>
|
||||
</tgroup>
|
||||
</table>
|
||||
|
|
@ -0,0 +1,29 @@
|
|||
#!/bin/bash
|
||||
# rand-string.sh
|
||||
# Generating an 8-character "random" string.
|
||||
|
||||
if [ "-n $1" ] # If command line argument present,
|
||||
then #+ then set start-string to it.
|
||||
str0="$1"
|
||||
else # Else use PID of script as start-string.
|
||||
str0="$$"
|
||||
fi
|
||||
|
||||
POS=2 # Starting from position 2 in the string.
|
||||
LEN=8 # Extract eight characters.
|
||||
|
||||
str1=$( echo "$str0" | md5sum | md5sum )
|
||||
# Doubly scramble: ^^^^^^ ^^^^^^
|
||||
|
||||
randstring="${str1:$POS:$LEN}"
|
||||
# Can parameterize ^^^^ ^^^^
|
||||
|
||||
echo "$randstring"
|
||||
|
||||
exit $?
|
||||
|
||||
# bozo$ ./rand-string.sh my-password
|
||||
# 1bdd88c4
|
||||
|
||||
# No, this is is not recommended
|
||||
#+ as a method of generating hack-proof passwords.
|
||||
|
|
@ -0,0 +1,25 @@
|
|||
#!/bin/bash
|
||||
# splitcopy.sh
|
||||
|
||||
# A script that splits itself into chunks,
|
||||
#+ then reassembles the chunks into an exact copy
|
||||
#+ of the original script.
|
||||
|
||||
CHUNKSIZE=4 # Size of first chunk of split files.
|
||||
OUTPREFIX=xx # csplit prefixes, by default,
|
||||
#+ files with "xx" ...
|
||||
|
||||
csplit "$0" "$CHUNKSIZE"
|
||||
|
||||
# Some comment lines for padding . . .
|
||||
# Line 15
|
||||
# Line 16
|
||||
# Line 17
|
||||
# Line 18
|
||||
# Line 19
|
||||
# Line 20
|
||||
|
||||
cat "$OUTPREFIX"* > "$0.copy" # Concatenate the chunks.
|
||||
rm "$OUTPREFIX"* # Get rid of the chunks.
|
||||
|
||||
exit $?
|
||||
Loading…
Reference in New Issue