seq

#!/bin/sh

######################################################################
#
# SEQ - A POSIX Compatible Implementation of the "seq" Command
#       Also Works on Just a POSIX Environment
#
# USAGE: seq [options] last
#        seq [options] first last
#        seq [options] first increment last
#
#        --by-myself .... (write as the 1st argument when use)
#                         Not use the "built-in" seq command and always
#                         do seq by myself but it is inferior to the
#                         built-in in performance
#        -f <format> .... Print all numbers using format.
#        -s <string> .... Separate numbers with string; default is a newline.
#        -w ............. Print all numbers with the same width, by padding
#                         with leading zeros.
#
# Written by Shell-Shoccar Japan (@shellshoccarjpn) on 2020-05-06
#
# This is a public-domain software (CC0). It means that all of the
# people can use this for any purposes with no restrictions at all.
# By the way, We are fed up with the side effects which are brought
# about by the major licenses.
#
# The latest version is distributed at the following page.
# https://github.com/ShellShoccar-jpn/misc-tools
#
######################################################################


######################################################################
# Initial Configuration
######################################################################

# === Initialize shell environment ===================================
set -u
umask 0022
export LC_ALL=C
export PATH="$(command -p getconf PATH 2>/dev/null)${PATH+:}${PATH-}"
case $PATH in :*) PATH=${PATH#?};; esac
export UNIX_STD=2003  # to make HP-UX conform to POSIX

# === Define the functions for printing usage and error message ======
print_usage_and_exit () {
  cat <<-USAGE 1>&2
	Usage   : ${0##*/} [options] last
	          ${0##*/} [options] first last
	          ${0##*/} [options] first increment last
	Arg&Opts: Almost compatible with GNU seq
	          The following options are available and compatible with it
	            -f <format>, -s <string>, -w
	          But --by-myself is the only original option, it prevent
	          from use the built-in same name command even if available
	Version : 2020-05-06 22:42:19 JST
	          (POSIX Bourne Shell/POSIX commands)
	            * Although the bult-in seq produces better performance
	              than the POSIX commands set
	USAGE
  exit 1
}
error_exit() {
  ${2+:} false && echo "${0##*/}: $2" 1>&2
  exit $1
}

# === Exec the built-in seq command if OK and exists =================
by_myself=0
case "${1:-}" in 
  '--by-myself')
     shift; by_myself=1
     ;;
  *) export mydir=$(d=${0%/*}/;[ "_$d" = "_$0/" ]||cd "$d";echo "$(pwd)")
     path0=${PATH:-}
     PATH=$(printf  '%s\n' "$path0"                |
            tr      ':' '\n'                       |
            awk     '$0!=ENVIRON["mydir"]{print;}' |
            tr      '\n' ':'                       |
            grep -v '^:$'                          |
            sed     's/:$//'                       )
     CMD_builtin=$(command -v seq 2>/dev/null || :)
     case "$CMD_builtin" in '') by_myself=1;; esac
     PATH=$path0
     unset mydir
     ;;
esac
case $by_myself in 0) exec "$CMD_builtin" ${1+"$@"}; exit 1;; esac


######################################################################
# Argument Parsing
######################################################################

# === Get the options and the filepath ===============================
# --- initialize option parameters -----------------------------------
optf=''
opts='\n'
optw=0
n_1st=1
n_inc=1
n_lst=''
#
# --- get them -------------------------------------------------------
optmode=''
while :; do
  case $# in 0) break;; esac
  case "$optmode" in
    '') case "$1" in
          -)       case $# in 1) break;; esac
                   ;;
          -[fsw]*) s=$(printf '%s\n' "${1#-}"                          |
                       awk '{f = "_"; s = "_"; w = "_"; err="";        #
                             l = length($0);                           #
                             for (n=1;n<=l;n++) {                      #
                               c = substr($0, n, 1);                   #
                               if      (c=="f") { f   = "f"; break; }  #
                               else if (c=="s") { s   = "s"; break; }  #
                               else if (c=="w") { w   = "w";        }  #
                               else             { err = "!";        }  #
                             }                                         #
                             arg = (n<l) ? substr($0,n+1) : "";        #
                             printf("%s%s%s%s %s",err,f,s,w,arg);    }')
                   arg=${s#* }
                   s=${s%% *}
                   case "$s" in '!'*) print_usage_and_exit;; esac
                   case "$s" in  *w*) optw=1              ;; esac
                   case "$s" in  *f*) optmode='f'         ;; esac
                   case "$s" in  *s*) optmode='s'         ;; esac
                   shift;
                   case "$arg" in '') continue;; esac
                   ;;
          --format=*)
                   optf=${s#--format=}
                   shift
                   continue
                   ;;
          --separator=*)
                   opts=${s#--format=}
                   shift
                   continue
                   ;;
          -[0-9]*) break
                   ;;
          -*)      print_usage_and_exit
                   ;;
          *)       break
                   ;;
        esac
        ;;
    *)  arg=$1
        shift
        ;;
  esac
  case "$optmode" in
    f) optf=$arg                ;;
    s) opts=$arg                ;;
    *) echo 'ERROR' 1>&2; exit 1;;
  esac
  optmode=''
done
case "$#" in
  1) n_lst=$1                    ;;
  2) n_1st=$1; n_lst=$2          ;;
  3) n_1st=$1; n_inc=$2; n_lst=$3;;
  *) 
esac

# === Vaidate arguments ==============================================
[ $optw -gt 0 ] && [ -n "$optf" ] && {
  error_exit 1 'format string may not be specified when printing equal width strings'
}
[ -n "$optf" ] && {
  printf '%s\n' "$optf" | grep -Eq '%(-?[0-9]+(\.[0-9]+)?)?[AaEeFfGg]' || {
    error_exit 1 'The format you gave me has no % directive'
  }
  case "$(printf '%s\n' "$optf" | sed 's/\%\(-\{0,1\}[0-9]\{1,\}\(\.[0-9]\{1,\}\)\{0,1\}\)\{0,1\}[AaEeFfGg%]//')" in
    *%*) error_exit 1 'The format you gave me is invalid or has too many % directives';;
    *)   :                                                                            ;;
  esac
}
n_pattern='^[+-]?[0-9]+(\.[0-9]+)?([eE][+-][0-9]{1,2})?$'
printf '%s\n' "$n_1st" | grep -Eq "$n_pattern" || {
  error_exit 1 '"first" floating point argument is invalid'
}
printf '%s\n' "$n_inc" | grep -Eq "$n_pattern" || {
  error_exit 1 '"increment" floating point argument is invalid'
}
printf '%s\n' "$n_lst" | grep -Eq "$n_pattern" || {
  error_exit 1 '"last" floating point argument is invalid'
}


######################################################################
# Make strings for AWK
######################################################################

# === Generate the format by "-w" ====================================
[ $optw -gt 0 ] && {
  optf=$(printf '%f %f %f' "$n_1st" "$n_inc" "$n_lst"               |
         grep -v 'Ee'                                               |
         tr   ' ' '\n'                                              |
         sed  '/\./s/0\{1,\}$//'                                    |
         sed  's/\.$//'                                             |
         sed  's/^\([+-]\{0,1\}\)0\{1,\}/\1/'                       |
         sed  's/^\([+-]\{0,1\}\)\./\10./'                          |
         sed  's/^\([+-]\{0,1\}\)$/\10/'                            |
         awk  'BEGIN {N=0; n=0;                                   } #
                     {p=index($1,".");                              #
                      i=length($0);                                 #
                      if (p>0) {j=i-p; i=p-1;}                      #
                      N=(i>N)?i:N; n=(j>n)?j:n;                   } #
               END   {if      (n>0) {printf("%%0%d.%df",N+1+n,n);}  #
                      else if (N>0) {printf("%%0%dd"   ,N      );}  #
                      else          {printf("%%g"              );}}')
}

# === Generate the format if not specified ===========================
[ -z "$optf" ] && {
  if printf '%s%s%s\n' "$n_1st" "$n_inc" "$n_lst" | grep -Eq '^[0-9]$'; then
    optf='%d'
  else
    optf='%g'
  fi
}

# === Convert the format string for AWK ==============================
optf=$( (printf '%s' "$optf";echo) |
        sed '$!s/$/\\n/'           |
        tr -d '\n'                 |
        grep  ^                    |
        sed 's/"/\\"/g'            )

# === Convert the "-s" option string for AWK =========================
opts=$( (printf '%s' "$opts";echo) |
        sed '$!s/$/\\n/'           |
        tr -d '\n'                 |
        grep  ^                    |
        sed 's/"/\\"/g'            )

# === Add a sign to the <increment> number ===========================
case "$n_inc" in [0-9.]*) n_inc="+$n_inc";; esac


######################################################################
# Main routine
######################################################################

# === Run "seq"-like script ==========================================
awk 'BEGIN{                                                 #
       if ('"$n_inc"' >= 0) {                               #
         # --- increment routine -------------------------- #
         if ('"$n_1st"' > '"$n_lst"') {exit;}               #
         i='"$n_1st"';                                      #
         printf("'"$optf"'", i);                            #
         i=i'"$n_inc"';                                     #
         for (            ; i<='"$n_lst"'; i=i'"$n_inc"') { #
           printf("%s'"$optf"'", "'"$opts"'", i);           #
         }                                                  #
       } else {                                             #
         # --- decrement routine -------------------------- #
         if ('"$n_1st"' < '"$n_lst"') {exit;}               #
         i='"$n_1st"';                                      #
         printf("'"$optf"'", i);                            #
         i=i'"$n_inc"';                                     #
         for (            ; i>='"$n_lst"'; i=i'"$n_inc"') { #
           printf("%s'"$optf"'", "'"$opts"'", i);           #
         }                                                  #
       }                                                    #
     }'                                                     |
grep ''


######################################################################
# Finish
######################################################################

exit 0