File: book.sh 1 #!/bin/sh 2 3 # The MIT License (MIT) 4 # 5 # Copyright © 2024 pacman64 6 # 7 # Permission is hereby granted, free of charge, to any person obtaining a copy 8 # of this software and associated documentation files (the “Software”), to deal 9 # in the Software without restriction, including without limitation the rights 10 # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 11 # copies of the Software, and to permit persons to whom the Software is 12 # furnished to do so, subject to the following conditions: 13 # 14 # The above copyright notice and this permission notice shall be included in 15 # all copies or substantial portions of the Software. 16 # 17 # THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 18 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 19 # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 20 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 21 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 22 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 23 # SOFTWARE. 24 25 26 # book [page-height...] [filenames...] 27 # 28 # Layout lines on 2 page-like side-by-side columns, just like a book. 29 # 30 # Book shows lays out text-lines the same way pairs of pages are laid out in 31 # books, letting you take advantage of wide screens. Every pair of pages ends 32 # with a special dotted line to visually separate it from the next pair. 33 # 34 # If you're using Linux or MacOS, you may find this cmd-line shortcut useful: 35 # 36 # # Like A Book lays lines as pairs of pages, the same way books do it 37 # lab() { book.sh "$(expr $(tput lines) - 1)" "$@" | less -KiCRS; } 38 39 40 # handle help options 41 case "$1" in 42 -h|--h|-help|--help) 43 # show help message, extracting the info-comment at the start 44 # of this file, and quit 45 awk '/^# +book/, /^$/ { gsub(/^# ?/, ""); print }' "$0" 46 exit 0 47 ;; 48 esac 49 50 awk ' 51 BEGIN { 52 # detect a leading number, and use it as a height value 53 if (ARGV[1] + 0 != 0) { 54 height = ARGV[1] + 0 55 delete ARGV[1] 56 } 57 58 # add the current screen height to negative height values 59 if (height < 0) { 60 "tput lines" | getline n 61 close("tput lines") 62 height += n 63 } 64 65 # use the current screen height minus 1, when a height either was not 66 # given explicitly, or is clearly too small 67 if (height < 2) { 68 "tput lines" | getline n 69 close("tput lines") 70 height = n - 1 71 } 72 73 # check if utf-8 strings need adapting when finding their width: 74 # this happens when `awk` is `mawk`, as is the default in debian; 75 # `mawk` does not count multi-byte UTF-8 symbols as single items 76 ascii_only = length("█") > 1 77 } 78 79 # expand all tabs, using 4 as the tabstop width; only takes 1 argument 80 function expand(s, n, l, res) { 81 if (s !~ "\t") return s 82 83 n = 0 84 res = "" 85 86 while (s != "") { 87 i = index(s, "\t") 88 if (i == 0) { 89 res = res s 90 return res 91 } 92 93 pre = substr(s, 1, i - 1) 94 s = substr(s, i + 1) 95 res = res pre 96 l = width(pre) 97 #l = length(pre) 98 n += l 99 100 switch (n % 4) { 101 case 0: 102 res = res " " 103 continue 104 case 1: 105 res = res " " 106 continue 107 case 2: 108 res = res " " 109 continue 110 case 3: 111 res = res " " 112 continue 113 } 114 } 115 116 return res 117 } 118 119 # remember all lines 120 { lines[NR] = expand($0) } 121 122 # width counts items in the string given, ignoring ANSI-style sequences 123 function width(s) { 124 gsub(/\x1b\[([0-9]*[A-HJKST]|[0-9;]*m)/, "", s) 125 # adapt string if running on `mawk`, as detected at the beginning: 126 # this is to force `mawk` to count multi-byte UTF-8 sequences as 127 # single items, by literally turning those into single-byte items 128 if (ascii_only) gsub(/[^\000-\177]{1,4}/, " ", s) 129 return length(s) 130 } 131 132 END { 133 step = height - 1 134 if (NR <= step) { 135 for (i in lines) print lines[i] 136 exit 137 } 138 139 for (i = 1; i <= NR; i += 2 * step) { 140 for (j = 0; j < step; j++) { 141 l = width(lines[i + j]) 142 if (maxl < l) maxl = l 143 l = width(lines[i + step + j]) 144 if (maxr < l) maxr = l 145 } 146 } 147 148 # make a separator wide enough to match the length of any output line 149 sep = "·" 150 widest = maxl + 3 + maxr 151 while (length(sep) < widest) sep = sep sep 152 # separator is used directly, so match the needed width exactly 153 sep = substr(sep, 1, widest) 154 155 # make enough spaces to hand-pad lines later; these spaces can exceed 156 # the max-count needed, since they are always subsliced when used later 157 spaces = " " 158 while (length(spaces) < widest) spaces = spaces spaces 159 160 # emit lines side by side 161 for (i = 1; i <= NR; i += 2 * step) { 162 # emit a page-bottom/separator line between page-pairs 163 if (i > 1) print sep 164 165 for (j = 0; j < step; j++) { 166 # avoid extra empty page-pair 167 if (i + j > NR) exit 168 169 l = lines[i + j] 170 r = lines[i + step + j] 171 172 #printf "%-*s █ %s\n", maxl, l, r 173 174 # pick/emit lines side by side; hand-pad left pages to align 175 # ANSI-styled text correctly 176 padl = substr(spaces, 1, maxl - width(l)) 177 printf "%s%s █ %s\n", l, padl, r 178 } 179 } 180 } 181 ' "$@"