Unix Utility Scripts

Utility Scripts for Unix-compatible systems (id est GNU/Linux). This page collects several of the scripts I've written for Linux over the years. Maybe someone else will find them useful.

execute a program in the background, redirect stdout and stderr to null, and keep it from being hungup. [Depends on: Bourne shell, coreutils]

#!/bin/sh
# ~/bin/amp
nohup "$@" > /dev/null 2>&1 &

Command line calculator based on bc, along with commonly used math functions. [Depends on: Bourne shell, bc]

#!/bin/sh
# ~/bin/calc
echo 'define ln(a) { return l(a); }
define exp(a) { return e(a); }
define pow(a,b) { return e(b*l(a)); }
define sqrtt(a) { return e(0.5*l(a)); }
define log(a) { return l(a)/l(10); }
define sin(a) { return s(a); }
define cos(a) { return c(a); }
define tan(a) { return s(a)/c(a); }
define sec(a) { return 1/c(a); }
define csc(a) { return 1/s(a); }
define cot(a) { return c(a)/s(a); }
define asin(x) { return a(x/sqrt(1-(x^2))); }
define acos(x) { return a(sqrt(1-(x^2))/x); }
define atan(x) { return a(x); }
define asec(x) { return a(sqrt((x^2)-1)); }
define acsc(x) { return a(1/sqrt((x^2)-1)); }
define acot(x) { return a(1/x);}
define sinh(x) { return (e(x)-e(-x))/2;}
define cosh(x) { return (e(x)+e(-x))/2;}
define tanh(x) { return (e(2*x) - 1)/(e(2*x) + 1); }
define asinh(x) { return l(x+sqrt((x^2)+1)); }
define acosh(x) { return l(x+sqrt((x^2)-1)); }
define atanh(x) { return 0.5*l((1+x)/(1-x)); }
pi = 4*a(1);
scale = 6;
' "$@" | bc -l

Make a file executeable. Saves keystrokes. [Depends on: Bourne shell, coreutils]

#!/bin/sh
# ~/bin/chx
chmod +x "$@"

Egg timer. Be sure to make something LOUD for your alarm; use sox to ajust the volume. [Depends on: Bourne shell, coreutils, mplayer]

#!/bin/sh
# EGG TIMER.  #DTPD#
# ${HOME}/bin/timer
MINUTES=$1
echo ${MINUTES}:00
for M in `seq -w $(($MINUTES - 1)) -1 0`; do
  for S in `seq -w 55 -5 0`; do
    sleep 5 ; echo ${M}:${S}
  done
done
echo -e "\n\n\t\tALARM! ALARM! ALARM!\n\n"
exec mplayer ~/Music/ALARM.mp3 &> /dev/null

Quickly update the system using yum. Yet another keystroke saver.[Depends on: Bourne shell, sudo, yum]

#!/bin/sh
# ~/bin/syyu
echo 'sudo yum -y update'
exec sudo yum -y update

A somewhat safer way to shred all the files in a directory. [Depends on: Bourne shell, coreutils, findutils]

#!/bin/sh
# ~/bin/rm-shred
{ for x in "$@" ; do
  # regular file
  find "$x" -type f -exec shred -u -n 1 {} \;
  # symlink
  find "$x" -type l -exec rm {} \;
  # wierd files
  find "$x" -type b -printf "%p is a block file"
  find "$x" -type c -printf "%p is a character file"
  find "$x" -type p -printf "%p is a named pipe"
  find "$x" -type s -printf "%p is a socket"
  # if we get here it is a directory or has been noted
  rm -r "$x"
done } 2> /dev/null

Safe File Removal [Depends on: Bourne shell, coreutils]

#!/bin/sh

## rms
##   "rm, safely." I also think it's funny
##   that I've named my reimplementation
##   of the MSFT recycling bin after RMS.
## (c) 2000-2003 Hal Canary
##
## License:
##   This is free software, see
##   http://www.gnu.org/licenses/gpl.txt
##   This product is distributed
##   WITHOUT ANY WARRANTY of any kind.

## TRASH=/tmp/$USER/trash
TRASH=${HOME}/tmp/Trash

if [ "$#" -lt 1 ]; then
  echo "Usage: $0 FILE";
  echo "Move FILE to $TRASH.";
  exit 1;
fi

test -d "$TRASH" || mkdir -pv $TRASH

for file in "$@"; do
  if [ -e "$file" ]; then
    mv -f -- "$file" $TRASH/
    echo "$file -> $TRASH/"
  else
    echo "Does $file exist?"
  fi
done
exit 0;

A terminal locker [Depends on: bash, coreutils]

#!/bin/sh
# ~/bin/tlock
PASS='12345' ; TRY=''
trap '' TERM INT
clear
while [ "$TRY" != "$PASS" ] ; do
  echo -en "\ntlock password: "
  stty -echo; read TRY; stty echo;
done
echo "";

Prepend a string to the beginning of each of a set of filename. [Depends on: Bourne shell, coreutils]

#!/bin/sh
# ~/bin/prepend-something
if [ "$#" -lt 2 ] ; then
 echo "useage:  $0 PREFEX FILE[S]"
 exit 1
fi
PREFEX=${1}
for argc in `seq 2 $#`; do
 eval arg=\${$argc}
 mv -v "${arg}" "${PREFEX}${arg}"
done

Make a Fair Use backup of a DVD that you own using mencoder. [Depends on: Bourne shell, coreutils, mencoder, mktemp]

#!/bin/sh
# ~/bin/rip-and-encode-dvd
X=`mktemp video-XXXXXXXXXX`
mv $X ${X}.avi
exec nice mencoder "dvd://1" -alang en \
 -slang en -o ${X}.avi -ovc lavc \
 -lavcopts "aspect=16/9:vcodec=mpeg4" \
 -oac copy 2> /dev/null

Print date+time in ISO 8601 format. [Depends on: Bourne shell, coreutils]

#!/bin/sh
# ~/bin/isodatetime
#date --rfc-3339=seconds
exec date +%Y-%m-%dT%T%z

Print just the date in ISO 8601 format. [Depends on: Bourne shell, coreutils]

#!/bin/sh
# ~/bin/isodate
exec date +%Y-%m-%d

Suppose you want to pipe something into a file as root using sudo. For example: sudo echo 1 > /proc/sys/net/ipv4/ip_forward ; this won't work. Instead try the sud script like this: sud 'echo 1 > /proc/sys/net/ipv4/ip_forward' . [Depends on: Bourne shell, coreutils, sudo]

#!/bin/sh
# ~/bin/sud
sudo su -c " $* "

Self-documented. [Depends on: Bourne shell, coreutils]

#!/bin/sh
# ~/bin/shorten
if [ "$#" -ne 1 ] ; then
 echo "useage:  shorten N"
 echo "   where N is a nonnegative integer"
 echo "   To print out the first N bytes of"
 echo "   the stdin to stdout."
 exit 1
fi
head -c $1
echo ""

Launch my favorite terminal editor. [Depends on: Bourne shell, emacs]

#!/bin/sh
# ~/bin/e
#exec nano "$@"
exec emacs -nw "$@"

Launch my favorite gui editor, gedit. [Depends on: Bourne shell, coreutils, gedit]

#!/bin/sh
# ~/bin/ge
nohup gedit "$@" > /dev/null 2>&1 &

sudo ifup [Depends on: Bourne shell, sudo, intiscripts]

#!/bin/sh
# ~/bin/u
sudo /sbin/ifup "$@"

sudo ifdown [Depends on: Bourne shell, sudo, intiscripts]

#!/bin/sh
# ~/bin/d
sudo /sbin/ifdown "$@"

[Depends on: Bourne shell, xorg-x11-apps, sudo, Linux kernel]

#!/bin/sh
# ~/bin/xconsole-proc-kmsg
sudo -b xconsole -file /proc/kmsg

Launch gthumb in the current directory if no argument. otherwise pass over all arguments. [Depends on: Bourne shell, gthumb]

#!/bin/sh
# ~/bin/gt
if [ "$#" -eq 0 ] ;  then
  echo gthumb . \> /dev/null 2\>\&1 \&
  gthumb . > /dev/null 2>&1 &
else
  echo gthumb "$@" \> /dev/null 2\>\&1 \&
  gthumb "$@" > /dev/null 2>&1 &
fi

Launch Evince [Depends on: Bourne shell, evince]

#!/bin/sh
# ~/bin/ev
evince "$@" > /dev/null 2>&1 &

Encrypt or decrypt with the ROT13 Cypher. Useage: rot13 Uryyb jbeyq. or echo Uryyb jbeyq. | rot13 . [Depends on: Bourne shell, coreutils]

#!/bin/sh
# ~/bin/rot13
if [ "$#" -gt 0 ] ; then
 echo "$@" | tr A-Za-z N-ZA-Mn-za-m
else
 tr A-Za-z N-ZA-Mn-za-m
fi

Grab a file over http and pipe it to stdout. [Depends on: Bourne shell, wget]

#!/bin/sh
# ~/bin/wgeto
exec wget -o /dev/null -O - "$@"

Extract a bunch of rar files. [Depends on: Bourne shell, unrar, coreutils]

#!/bin/sh
# ~/bin/unrar-extract
for x in "$@" ; do
 nice unrar x "$x"
done

List only directories. [Depends on: Bourne shell, grep, coreutils]

#!/bin/sh
# ~/bin/lsd
/bin/ls --color='yes' -l "$@" | grep "^d"
# /bin/ls --color=yes -p "$@" | grep "/$"

Generate Password. Self-documented. [Depends on: Bourne shell, Linux kernel, coreutils, sed]

#!/bin/sh
# ~/bin/genpasswd
#   Generate a random password with about
#   142 bits of randomness, making use of
#   /dev/random.
# Note:
#   Most online services have somewhat
#   arbitrary rules about what characters
#   can be included in a password. So we
#   limit ourselves to A-Za-z0-9.
# Copyright 2007 Hal Canary
# Dedicated to the Public Domain.
echo "Grabbing bits from /dev/random..." 1>&2
head -c 18 /dev/random | base64 | \
 sed 's/\//Z/g;s/+/z/g;'
# If you lack base64 on your system, try:
# head -c 18 /dev/random  | uuenview -b '' | \
#   sed 's/\//Z/g;s/+/z/g;'

Convert mp3 files to CD-Audio. [Depends on Bourne Shell, coreutils, lame, sox.]

#!/bin/sh

# ~/bin/makecdrfiles

# Convert mp3s to .cdr format for an audio CD.
# Copyright 2000-2007 Hal Canary
# Dedicated to the Public Domain.

if [ "$#" -lt 1 ] ; then
  echo "  Useage: $0 file.mp3 [more files.mp3]"
  echo ""
  echo "  After you're done, burn with:"
  echo -n '   sudo cdrecord -v -dao -eject dev=$DEV'
  echo ' -pad -audio *.cdr'
  exit 1
fi
for FILE in "$@" ; do
  nice lame --decode "$FILE" - | \
    nice sox -t wav - "$(basename $FILE .mp3).cdr"
done