index() #@ Print the position of $2 in $1
{ #@ USAGE: index STRING SUBSTRING
local idx
case $1 in
*$2*) idx=${1%%$2*}
echo $(( ${#idx} + 1 )) ;;
*) echo 0 ;;
esac
}

From Article

die() #@ Exit with error code and optional message
{ #@ USAGE: die RETURN_CODE [MESSAGE]
result=$1
shift
[ -n "$*" ] && printf "%s\n" "$*" >&2
exit "$result"
}

From Article

overlay() #@ Place SUBSTRING over STRING beginning at OFFSET 
{ #@ USAGE: overlay VARNAME SUBSTRING OFFSET 
local varname=$1 substr=$2 start=$3 string 
eval "string=\${$varname}" 
left=${string:0:start} 
right=${string:start+${#substr}} 
printf -v "$varname" %s%s%s "$left" "$substr" "$right" 
}

From Article

asc() #@ Print the ASCII value of the first character of each argument 
{ #@ USAGE: asc STRING ... 
for char 
do 
printf "%d${EOV-\n}" "'$char" 
done
}

From Article

revword() #@ print each argument with bytes reversed
for w
do
len=${#w}
w2=
n=0
while (( ${#w2} < len ))
do
w2=${w:n++:1}$w2
done
printf "%s\n" "$w2"
done

From Article

addpath() #@ add directory or directories to $PATH
{ #@ USAGE: addpath DIR ...
local prefix=0 quiet=0 OPTIND=1 p
 
while getopts iq var
do
case "$var" in
i) prefix=1 ;;
q) quiet=1 ;;
esac
done
shift $(( $OPTIND - 1 ))
 
for p
do
p=${p%"${p##*[!/]}"} ## remove trailing slashes
case $p in
""|.) continue ;;
esac
case :$PATH: in
*:$p:*)
(( quiet == 0 )) && echo "addpath: $p already in path" >&2
continue
;;
esac
if [ -d "$p" ]
then
(( prefix == 1 )) && PATH=$p:$PATH || PATH=$PATH:$p
else
[ $quiet -eq 0 ] && echo "addpath: $p is not a directory" >&2
fi
done
export PATH ## probably unnecessary
}

From Article

random_date() #@ Return random date in given range of years
{ #@ USAGE: random_date FIRST LAST [VAR]
#@ Global variables set: random_date [VAR]
local first=${1:-1752} last=${2:-2100} var=$3
declare -i year month day dim
year=$(( RANDOM % (last-first) + first ))
month=$(( RANDOM % 12 + 1 ))
days_in_month dim "$month" "$year"
day=$(( RANDOM % dim + 1 ))
printf -v random_date "%d-%02d-%02d" "$year" "$month" "$day"
is_var "$var" &&
printf -v "$var" %s "$random_date" ||
printf "%s\n" "$random_date"
}

From Article

is_factor() #@ Return successfully if $2 is a factor of $1
{ #@ USAGE: is_factor NUMBER FACTOR
local number=$1 factor=$2
(( ((number / factor) * factor) == number ))
}

From Article

dec2bin() #@ Convert decimal integer to binary optionally padding with zeroes 
{ #@ USAGE: dec2bin INT [WIDTH] [VAR] 
local val=$1 _w=$2 var=$3 _b=2 _r bin 
if (( $# == 1 )) || is_var "$2" ## is_var() posted last month 
then 
_w=1 
fi 
while ((val)) 
do 
_r=$(( $val % $_b )) 
bin=$_r$bin; 
val=$(( val / _b )) 
done 
printf -v bin "%0${_w}d" "$((10#$bin))" 
is_var "$var" && printf -v "$var" %s "$bin" || printf "%s\n" "$bin" 
}

From Article

psg() #@ Show all running processes matching ARG[s]
{ #@ USAGE: psg STRING ...
local ss
for ss
do
## Enclose first character in brackets so grep doesn't show its own process
ss=\[${ss:0:1}\]${ss#?}
ps -ef | grep "$ss"
[ $# -gt 1 ] && echo
done
}

From Article

calc() #@ Print the result of arithmetical calulation
{ #@ USAGE: calc EXPRESSION
awk 'BEGIN {print '"${*//x/*}"'}'
}

From Article

lines() #@ Print lines on screen descending from the current point
{ #@ USAGE: [printat ROW COL [STRING];] lines STRING ...
local cu_save=$'\e[s' cu_restore=$'\e[u' cu_down=$'\e[B'
printf "$cu_restore$cu_down$cu_save%s" "$@"
}

From Article

case ${1#-} in 
*[!0-9.]*|.) echo not an integer or float ;; 
*.*) echo float ;; 
*) echo int ;; 
esac

- OR -

i=$1 
let 'i++' 
 
if [ $? -eq 0 ] # check in not error returned 
then 
echo "integer" 
else 
echo "not integer" 
fi

From Article

fpmul() #@ Perform floating-point multiplication in the shell
{ #@ USAGE: fpmul [VAR] NUM.DEC ...
local _var= _places _tot _neg _n _int _dec _df _fpmul
if [[ ${1^^} =~ ^[A-Z_][A-Z0-9_]*$ ]]
then
_var=$1
shift
fi
_places=
_tot=1
_neg=
for _n
do
## 2 negatives make a positive
case $_n in
-*) [ "$_neg" = '-' ] && _neg= || _neg='-'
_n=${_n#-}
;;
esac
 
## Check for non-numeric characters
case $_n in
*[!0-9.]*) return 1 ;;
esac
 
## count the number of decimal _places,
## then remove the decimal point
case $_n in
.*) _int=
_dec=${_n#?}
_places=$_places$_dec
_n=$_dec
;;
*.*) _dec=${_n#*.}
_int=${_n%.*}
_places=$_places$_dec
_n=$_int$_dec
;;
esac
 
## remove leading zeroes
while :
do
case $_n in
""|0) _n=0
_fpmul=0
return
;;
0*) _n=${_n#0} ;;
*) break;;
esac
done
 
## multiply by the previous _total
_tot=$(( $_tot * ${_n:-0} ))
 
## report any overflow error
case $_tot in
-*) printf "fpmul: overflow error: %s\n" "$_tot" >&2
return 1
;;
esac
done
 
while [ ${#_tot} -lt ${#_places} ]
do
_tot=0$_tot
done
 
_df=
while [ ${#_df} -lt ${#_places} ]
do
left=${_tot%?}
_df=${_tot#$left}$_df
_tot=$left
done
_fpmul=$_tot${_df:+.$_df}
 
## remove trailing zeroes or decimal points
while :
do
case $_fpmul in
*.*[0\ ]|*.) _fpmul=${_fpmul%?} ;;
.*) _fpmul=0$_fpmul ;;
*) break ;;
esac
done
 
[[ $_var ]] &&
printf -v "$_var" %s "$_fpmul" ||
printf '%s\n' "$_fpmul"
}
num.dec

From article

ashow() #@ Display contents of array[s]
{ #@ USAGE: ashow ARRAYNAME ...
local _arg _num=0
for arg
do
:; ((_num++)) && echo
:; declare -n array=$arg
:; [[ -n ${array[*]} ]] && printf '%s\n' "${array[@]}"
done
}

From Article

revword() #@ Reverse the order of characters in STRING
{ #@ USAGE: revword STRING [VAR]
local _n _word=$1 _var=$2 _len _r _rw= _l
while read -n1 _l
do
_rw=$_l$_rw
done <<< "$_word"
[[ ${_var^^} =~ ^[A-Z_][A-Z0-9_]*$ ]] &&
printf -v "$_var" %s "$_rw" ||
printf '%s\n' "$_rw"
}

From Article

trim() #@ Trim spaces (or char in $2) from both ends of $1
{ #@ USAGE: trim STRING [CHAR [VAR]]
local _trim_string _trim=$1 _char=${2:- } _var=$3
_trim_string=${_trim##*[!$_char]}
_trim=${_trim%"$_trim_string"}
_trim_string=${_trim%%[!$_char]*}
_trim=${_trim#"$_trim_string"}
is_var "$_var" &&
printf -v "$_var" %s "$_trim" ||
printf '%s\n' "$_trim"
}

From Article