edited pr, fold and fmt chapters

Author: learnbyexample

fold-fmt.html

@@ -38,16 +38,16 @@
                     Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
                         link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
                     });
-                </script><div id=content class=content><main><div class=sidetoc><nav class=pagetoc></nav></div><h1 id=fold-and-fmt><a class=header href=#fold-and-fmt>fold and fmt</a></h1><p>These two commands are useful to split and join lines to meet a specific line length requirement. <code>fmt</code> is smarter and usually the tool you want, but <code>fold</code> can be handy for some cases.<h2 id=fold><a class=header href=#fold>fold</a></h2><p>By default, <code>fold</code> will wrap lines that are greater than <code>80</code> bytes long, which can be customized using the <code>-w</code> option. You might wonder if there are tasks where wrapping without context could be useful. One use case I can think of is the <a href=https://en.wikipedia.org/wiki/FASTA_format>FASTA format</a>.<pre><code class=language-bash>$ cat greeting.txt
+                </script><div id=content class=content><main><div class=sidetoc><nav class=pagetoc></nav></div><h1 id=fold-and-fmt><a class=header href=#fold-and-fmt>fold and fmt</a></h1><p>These two commands are useful to split and join lines to meet a specific line length requirement. <code>fmt</code> is smarter and usually the tool you want, but <code>fold</code> can be handy for some cases.<h2 id=fold><a class=header href=#fold>fold</a></h2><p>By default, <code>fold</code> will wrap lines that are greater than <code>80</code> bytes long, which can be customized using the <code>-w</code> option. The newline character isn't part of this line length calculation. You might wonder if there are tasks where wrapping without context could be useful. One use case I can think of is the <a href=https://en.wikipedia.org/wiki/FASTA_format>FASTA format</a>.<pre><code class=language-bash>$ cat greeting.txt
 Hi there
 Have a nice day
 
-# second line is greater than 10 bytes
+# splits second line since it is greater than 10 bytes
 $ fold -w10 greeting.txt
 Hi there
 Have a nic
 e day
-</code></pre><p>The <code>-s</code> option will look for spaces to break before the maximum width allowed.<pre><code class=language-bash>$ fold -s -w10 greeting.txt
+</code></pre><p>The <code>-s</code> option looks for the presence of spaces to determine the line splitting. This check is performed within the limits of the wrap length.<pre><code class=language-bash>$ fold -s -w10 greeting.txt
 Hi there
 Have a 
 nice day
@@ -86,8 +86,24 @@
 </code></pre><p>Unlike <code>fold</code>, words are not split even if they exceed the maximum line width. Another difference is that <code>fmt</code> will add a final newline character if it isn't present in the input.<pre><code class=language-bash>$ printf 'hi there' | fmt -w4
 hi
 there
-</code></pre><p>The <code>fmt</code> command also allows you to join lines together that are shorter than the specified width. As mentioned before, paragraphs are taken into consideration, so empty lines will prevent merging. The <code>-s</code> option will disable line merging.<pre><code class=language-bash># first 4 characters of sample.txt are ignored here,
-# since line numbering will hinder lines being merged
+</code></pre><p>The <code>fmt</code> command also allows you to join lines together that are shorter than the specified width. As mentioned before, paragraphs are taken into consideration, so empty lines will prevent merging. The <code>-s</code> option will disable line merging.<pre><code class=language-bash>$ cat sample.txt
+ 1) Hello World
+ 2) 
+ 3) Hi there
+ 4) How are you
+ 5) 
+ 6) Just do-it
+ 7) Believe it
+ 8) 
+ 9) banana
+10) papaya
+11) mango
+12) 
+13) Much ado about nothing
+14) He he he
+15) Adios amigo
+
+# 'cut' here helps to ignore first 4 characters of sample.txt
 $ cut -c5- sample.txt | fmt -w30
 Hello World
 

paste.html

@@ -109,7 +109,7 @@
 1       3.14    2
 3       42      4
 5       1000    6
-</code></pre><p>If you don't want to manually type the number of <code>-</code> required, you can use the below <code>printf</code> trick<pre><code class=language-bash># the string before %.s is repeated based on the number of arguments
+</code></pre><p>If you don't want to manually type the number of <code>-</code> required, you can use this <code>printf</code> trick:<pre><code class=language-bash># the string before %.s is repeated based on the number of arguments
 $ printf 'x %.s' a b c
 x x x 
 $ printf -- '- %.s' {1..5}

pr.html

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                     Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
                         link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
                     });
-                </script><div id=content class=content><main><div class=sidetoc><nav class=pagetoc></nav></div><h1 id=pr><a class=header href=#pr>pr</a></h1><blockquote><p>Paginate or columnate FILE(s) for printing.</blockquote><p>As stated in the above quote from the manual, the <code>pr</code> command is mainly used for two tasks. This book will discuss only the columnate features and some miscellaneous tasks.<p>Here's a pagination example if you are interested in exploring further. The <code>pr</code> command will add blank lines, a header and so on to make it suitable for printing.<pre><code class=language-bash>$ pr greeting.txt | head
+                </script><div id=content class=content><main><div class=sidetoc><nav class=pagetoc></nav></div><h1 id=pr><a class=header href=#pr>pr</a></h1><blockquote><p>Paginate or columnate FILE(s) for printing.</blockquote><p>As stated in the above quote from the manual, the <code>pr</code> command is mainly used for those two tasks. This book will discuss only the columnate features and some miscellaneous tasks.<p>Here's a pagination example if you are interested in exploring further. The <code>pr</code> command will add blank lines, a header and so on to make it suitable for printing.<pre><code class=language-bash>$ pr greeting.txt | head
 
 
 2021-08-05 14:10                   greeting.txt                   Page 1
@@ -88,7 +88,7 @@
 9,10,,
 </code></pre><h2 id=customizing-page-width><a class=header href=#customizing-page-width>Customizing page width</a></h2><p>As mentioned before, the default page width is <code>72</code>. This can cause lines to be truncated, unless <code>-s</code> or <code>-J</code> options are used. There's another issue you might run into, for example:<pre><code class=language-bash>$ seq 100 | pr -50ats,
 pr: page width too narrow
-</code></pre><p><code>(N-1)*length(separator) + N</code> is the minimum page width you need, where <code>N</code> is the number of columns required. So, for <code>50</code> columns and a separator of length <code>1</code>, you'll need a minimum width of <code>99</code>. This calculation doesn't make any assumption about the size of input lines, so you'll need <code>-J</code> to ensure input lines aren't truncated.<p>You can use the <code>-w</code> option to change the page width. This option will truncate lines, so use <code>-J</code> option as well unless you really need truncation. If truncation is active, maximum column width is <code>(PageWidth - (N-1)*length(separator)) / N</code> rounded down to an integer value. Here's some examples:<pre><code class=language-bash># minimum width needed is 3 for N=2 and length=1
+</code></pre><p><code>(N-1)*length(separator) + N</code> is the minimum page width you need, where <code>N</code> is the number of columns required. So, for <code>50</code> columns and a separator of length <code>1</code>, you'll need a minimum width of <code>99</code>. This calculation doesn't make any assumption about the size of input lines, so you may need <code>-J</code> to ensure input lines aren't truncated.<p>You can use the <code>-w</code> option to change the page width. The <code>-w</code> option overrides the effect of <code>-s</code> option on line truncation, so use <code>-J</code> option as well unless you really need truncation. If truncation is active, maximum column width is <code>(PageWidth - (N-1)*length(separator)) / N</code> rounded down to an integer value. Here's some examples:<pre><code class=language-bash># minimum width needed is 3 for N=2 and length=1
 # maximum column width: (6 - 1) / 2 = 2
 $ pr -w6 -2ts, greeting.txt
 Hi,Ha
@@ -121,7 +121,7 @@
 1 : 4
 2 : 5
 3 : 6
-</code></pre><p>You can prefix the output with line numbers using the <code>-n</code> option. By default, this option supports up to <code>5</code> digit numbers and uses the tab character to separate the line contents. You can optionally pass two arguments to this option — maximum number of digits and the separator character. If both arguments are used, the separator should be specified first. If you want to customize the starting line number, use the <code>-N</code> option as well.<pre><code class=language-bash># maximum of 1 digit for numbering
+</code></pre><p>You can prefix the output with line numbers using the <code>-n</code> option. By default, this option supports up to <code>5</code> digit numbers and uses the tab character to separate the numbering and line contents. You can optionally pass two arguments to this option — maximum number of digits and the separator character. If both arguments are used, the separator should be specified first. If you want to customize the starting line number, use the <code>-N</code> option as well.<pre><code class=language-bash># maximum of 1 digit for numbering
 # use : as the separator between line number and line contents
 $ pr -n:1 -mts, colors_1.txt colors_2.txt
 1:Blue,Black
@@ -133,14 +133,15 @@
 7:White,White
 </code></pre><p>The string passed to <code>-s</code> is treated literally. Depending on your shell you can use <a href=https://www.gnu.org/software/bash/manual/html_node/ANSI_002dC-Quoting.html>ANSI-C quoting</a> to allow escape sequences. Unlike columnate, the separator is added even if the data is missing for some of the files.<pre><code class=language-bash># greeting.txt has 2 lines
 # fruits.txt has 3 lines
+# same as: paste -d$'\n' greeting.txt fruits.txt
 $ pr -mts$'\n' greeting.txt fruits.txt
 Hi there
 banana
 Have a nice day
 papaya
 
 mango
-</code></pre><h2 id=miscellaneous><a class=header href=#miscellaneous>Miscellaneous</a></h2><p>You can use the <code>-d</code> option to double space the input. That is, every newline character is doubled.<pre><code class=language-bash>$ pr -dt fruits.txt
+</code></pre><h2 id=miscellaneous><a class=header href=#miscellaneous>Miscellaneous</a></h2><p>You can use the <code>-d</code> option to double space the input contents. That is, every newline character is doubled.<pre><code class=language-bash>$ pr -dt fruits.txt
 banana
 
 papaya
@@ -150,8 +151,8 @@
 </code></pre><p>The <code>-v</code> option will convert non-printing characters like carriage return, backspace, etc to their octal representations (<code>\NNN</code>).<pre><code class=language-bash>$ printf 'car\bt\r\nbike\0p\r\n' | pr -vt
 car\010t\015
 bike\000p\015
-</code></pre><p><code>pr -t</code> is a roundabout way of concatenating input files. But one advantage is that this will add a newline character at the end if not present in the input.<pre><code class=language-bash># cat will not add a newline character
-# so, use pr if newline is needed at the end
+</code></pre><p><code>pr -t</code> is a roundabout way of concatenating input files. But one advantage is that this will add a newline character at the end if not present in the input.<pre><code class=language-bash># 'cat' will not add a newline character
+# so, use 'pr' if newline is needed at the end
 $ printf 'a\nb\nc' | pr -t
 a
 b