examples/scripts/line-input.bash

   1 #! /bin/bash
   2 #
   3 #From: kaz@cafe.net (Kaz Kylheku)
   4 #Newsgroups: comp.unix.shell
   5 #Subject: Funky little bash script
   6 #Message-ID: <6mspb9$ft2@espresso.cafe.net>
   7 #Date: Thu, 25 Jun 1998 06:11:39 GMT
   8
   9 #Here is something I wrote a few years ago when I was bored one day.
  10 #Warning: this contains control characters.
  11
  12 # Line input routine for GNU Bourne-Again Shell
  13 # plus terminal-control primitives.
  14 #
  15 # by Kaz Kylheku
  16 # June 1996, Vancouver, Canada
  17
  18
  19 #
  20 # Function to disable canonical input processing.
  21 # Terminal modes are saved into variable "savetty"
  22 #
  23 #
  24
  25 function raw
  26 {
  27         savetty=$(stty -g)
  28         stty -icanon -isig -echo -echok -echonl inlcr
  29 }
  30
  31 #
  32 # Function to restore terminal settings from savetty variable
  33 #
  34
  35 function restore
  36 {
  37         stty $savetty
  38 }
  39
  40 #
  41 # Set terminal MIN and TIME values.
  42 # If the input argument is a zero, set up terminal to wait for
  43 # a keystroke indefinitely. If the argument is non-zero, set up
  44 # an absolute timeout of that many tenths of a second. The inter-keystroke
  45 # timer facility of the terminal driver is not exploited.
  46 #
  47
  48 function settimeout
  49 # $1 = tenths of a second
  50 {
  51         if [ "$1" = "0" ] ; then
  52                 min=1
  53                 timeout=0
  54         else
  55                 min=0
  56                 timeout="$1"
  57         fi
  58
  59         stty min $min time $timeout
  60
  61         unset min timeout
  62 }
  63
  64 #
  65 # Input a single key using 'dd' and echo it to standard output.
  66 # Launching an external program to get a single keystroke is a bit
  67 # of a pig, but it's the best you can do! Maybe we could convince the
  68 # GNU guys to make 'dd' a bash builtin.
  69 #
  70
  71 function getkey
  72 {
  73         eval $1="\"\$(dd bs=1 count=1 2> /dev/null)\""
  74 }
  75
  76 #
  77 # Input a line of text gracefully.
  78 # The first argument is the name of a variable where the input line is
  79 # to be stored. If this variable is not empty, its contents are printed
  80 # and treated as though the user had entered them.
  81 # The second argument gives the maximum length of the input line; if it
  82 # is zero, the input is unlimited (bad idea).
  83 # ^W is used to delete words
  84 # ^R redraws the line at any time by backspacing over it and reprinting it
  85 # ^U backspaces to the beginning
  86 # ^H or ^? (backspace or del) delete a single character
  87 # ^M (enter) terminates the input
  88 # all other control keys are ignored and cause a beep when pressed
  89 #
  90 #
  91
  92
  93 function getline
  94 {
  95         settimeout 0                    # No keystroke timeout.
  96         save_IFS="$IFS"                 # Save word delimiter and set it to
  97         IFS=""                          # to null so ${#line} works correctly.
  98         eval line=\${$1}                # Fetch line contents
  99         echo -n "$line"                 # and print the existing line.
 100         while [ 1 ] ; do
 101                 getkey key              # fetch a single keystroke
 102                 case "$key" in
 103                 \b | \x7f )                         # BS or DEL
 104                         if [ ${#line} != 0 ] ; then     # if line not empty
 105                                 echo -n "\b \b"           # print destructive BS
 106                                 line="${line%%?}"       # chop last character
 107                         else                            # else if line empty
 108                                 echo -n \a               # beep the terminal
 109                         fi
 110                         ;;
 111                 \x15 )                                     # kill to line beg
 112                         while [ ${#line} != 0 ] ; do    # while line not empty
 113                                 echo -n "\b \b"           # print BS, space, BS
 114                                 line="${line%?}"        # shorten line by 1
 115                         done
 116                         ;;
 117                 \x12 )                                     # redraw line
 118                         linesave="$line"                # save the contents
 119                         while [ ${#line} != 0 ] ; do    # kill to line beg
 120                                 echo -n "\b \b"
 121                                 line="${line%?}"
 122                         done
 123                         echo -n "$linesave"             # reprint, restore
 124                         line="$linesave"
 125                         unset linesave                  # forget temp var
 126                         ;;
 127                 \x17 )
 128                         while [ "${line% }" != "$line" ] && [ ${#line} != 0 ] ; do
 129                                 echo -n "\b \b"
 130                                 line="${line%?}"
 131                         done
 132                         while [ "${line% }" = "$line" ] && [ ${#line} != 0 ] ; do
 133                                 echo -n "\b \b"
 134                                 line="${line%?}"
 135                         done
 136                         ;;
 137                 \x7f | \x01 | \x02 | \x03 | \x04 | \x05 | \x06 | \a | \b | \v | \f | 
 )
 138                         echo -n \a       # ignore various control characters
 139                         ;;              # with an annoying beep
 140                 \x0e | \x0f | \x10 | \x11 | \x12 | \x13 | \x14 | \x15 | \x16 | \x17 | \x18 | \x19 | \x1a )
 141                         echo -n \a
 142                         ;;
 143                 '       ' | \e | \x1d | \x1e | \x1f | \x1c )
 144                         echo -n \a
 145                         ;;
 146                 '' )                    # Break out of loop on carriage return.
 147                         echo            # Send a newline to the terminal.
 148                         break           # (Also triggered by NUL char!).
 149                         ;;
 150                 * )             # Append character to the end of the line.
 151                                 # If length is restricted, and the line is too
 152                                 # long, then beep...
 153
 154                         if [ "$2" != 0 ] && [ $(( ${#line} >= $2 )) = 1 ] ; then
 155                                 echo -n \a
 156                         else                            # Otherwise add
 157                                 line="$line$key"        # the character.
 158                                 echo -n "$key"          # And echo it.
 159                         fi
 160                         ;;
 161                 esac
 162         done
 163         eval $1=\"\$line\"
 164         IFS="$save_IFS"
 165         unset line save_IFS
 166 }
 167
 168 # uncomment the lines below to create a standalone test program
 169 #
 170 echo "Line input demo for the GNU Bourne-Again Shell."
 171 echo "Hacked by Kaz Kylheku"
 172 echo
 173 echo "Use ^H/Backspace/Del to erase, ^W to kill words, ^U to kill the"
 174 echo "whole line of input, ^R to redraw the line."
 175 echo "Pass an argument to this program to prime the buffer contents"
 176 raw
 177 echo -n "go: "
 178 if [ ${#1} != 0 ] ; then
 179         LINE=$1
 180 fi
 181 getline LINE 50
 182 restore
 183
 184 echo "<$LINE>"