ASCII Table

Advanced Bash-Scripting Guide:
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# Appendix T. ASCII Table

Traditionally, a book of this sort has an ASCII Table appendix. This book does not. Instead, here are several short scripts, each of which generates a complete ASCII table.

Example T-1. A script that generates an ASCII table

    #!/bin/bash
    # ascii.sh
    # ver. 0.2, reldate 26 Aug 2008
    # Patched by ABS Guide author.

    # Original script by Sebastian Arming.
    # Used with permission (thanks!).

    exec >ASCII.txt         #  Save stdout to file,
                            #+ as in the example scripts
                            #+ reassign-stdout.sh and upperconv.sh.

    MAXNUM=256
    COLUMNS=5
    OCT=8
    OCTSQU=64
    LITTLESPACE=-3
    BIGSPACE=-5

    i=1 # Decimal counter
    o=1 # Octal counter

    while [ "$i" -lt "$MAXNUM" ]; do  # We don't have to count past 400 octal.
            paddi="    $i"
            echo -n "${paddi: $BIGSPACE}  "       # Column spacing.
            paddo="00$o"
    #       echo -ne "\\${paddo: $LITTLESPACE}"   # Original.
            echo -ne "\\0${paddo: $LITTLESPACE}"  # Fixup.
    #                   ^
            echo -n "     "
            if (( i % $COLUMNS == 0)); then       # New line.
               echo
            fi
            ((i++, o++))
            # The octal notation for 8 is 10, and 64 decimal is 100 octal.
            (( i % $OCT == 0))    && ((o+=2))
            (( i % $OCTSQU == 0)) && ((o+=20))
    done

    exit $?

    # Compare this script with the "pr-asc.sh" example.
    # This one handles "unprintable" characters.

    # Exercise:
    # Rewrite this script to use decimal numbers, rather than octal.

Example T-2. Another ASCII table script

    #!/bin/bash
    # Script author: Joseph Steinhauser
    # Lightly edited by ABS Guide author, but not commented.
    # Used in ABS Guide with permission.

    #-------------------------------------------------------------------------
    #-- File:  ascii.sh    Print ASCII chart, base 10/8/16         (JETS-2012)
    #-------------------------------------------------------------------------
    #-- Usage: ascii [oct|dec|hex|help|8|10|16]
    #--
    #-- This script prints out a summary of ASCII char codes from Zero to 127.
    #-- Numeric values may be printed in Base10, Octal, or Hex.
    #--
    #-- Format Based on: /usr/share/lib/pub/ascii with base-10 as default.
    #-- For more detail, man ascii . . .
    #-------------------------------------------------------------------------

    [ -n "$BASH_VERSION" ] && shopt -s extglob

    case "$1" in
       oct|[Oo]?([Cc][Tt])|8)       Obase=Octal;  Numy=3o;;
       hex|[Hh]?([Ee][Xx])|16|[Xx]) Obase=Hex;    Numy=2X;;
       help|?(-)[h?])        sed -n '2,/^[ ]*$/p' $0;exit;;
       code|[Cc][Oo][Dd][Ee])sed -n '/case/,$p'   $0;exit;;
       *) Obase=Decimal
    esac # CODE is actually shorter than the chart!

    printf "\t\t## $Obase ASCII Chart ##\n\n"; FM1="|%0${Numy:-3d}"; LD=-1

    AB="nul soh stx etx eot enq ack bel bs tab nl vt np cr so si dle"
    AD="dc1 dc2 dc3 dc4 nak syn etb can em sub esc fs gs rs us sp"

    for TOK in $AB $AD; do ABR[$((LD+=1))]=$TOK; done;
    ABR[127]=del

    IDX=0
    while [ $IDX -le 127 ] && CHR="${ABR[$IDX]}"
       do ((${#CHR}))&& FM2='%-3s'|| FM2=`printf '\\\\%o  ' $IDX`
          printf "$FM1 $FM2" "$IDX" $CHR; (( (IDX+=1)%8))||echo '|'
       done

    exit $?

Example T-3. A third ASCII table script, using awk

    #!/bin/bash
    # ASCII table script, using awk.
    # Author: Joseph Steinhauser
    # Used in ABS Guide with permission.

    #-------------------------------------------------------------------------
    #-- File:  ascii     Print ASCII chart, base 10/8/16         (JETS-2010)
    #-------------------------------------------------------------------------
    #-- Usage: ascii [oct|dec|hex|help|8|10|16]
    #--
    #-- This script prints a summary of ASCII char codes from Zero to 127.
    #-- Numeric values may be printed in Base10, Octal, or Hex (Base16).
    #--
    #-- Format Based on: /usr/share/lib/pub/ascii with base-10 as default.
    #-- For more detail, man ascii
    #-------------------------------------------------------------------------

    [ -n "$BASH_VERSION" ] && shopt -s extglob

    case "$1" in
       oct|[Oo]?([Cc][Tt])|8)       Obase=Octal;  Numy=3o;;
       hex|[Hh]?([Ee][Xx])|16|[Xx]) Obase=Hex;    Numy=2X;;
       help|?(-)[h?])        sed -n '2,/^[ ]*$/p' $0;exit;;
       code|[Cc][Oo][Dd][Ee])sed -n '/case/,$p'   $0;exit;;
       *) Obase=Decimal
    esac
    export Obase   # CODE is actually shorter than the chart!

    awk 'BEGIN{print "\n\t\t## "ENVIRON["Obase"]" ASCII Chart ##\n"
               ab="soh,stx,etx,eot,enq,ack,bel,bs,tab,nl,vt,np,cr,so,si,dle,"
               ad="dc1,dc2,dc3,dc4,nak,syn,etb,can,em,sub,esc,fs,gs,rs,us,sp"
               split(ab ad,abr,",");abr[0]="nul";abr[127]="del";
               fm1="|%0'"${Numy:- 4d}"' %-3s"
               for(idx=0;idx<128;idx++){fmt=fm1 (++colz%8?"":"|\n")
               printf(fmt,idx,(idx in abr)?abr[idx]:sprintf("%c",idx))} }'

    exit $?

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