edited cut, paste, seq and shuf chapters

Author: learnbyexample

cut.html

@@ -38,21 +38,21 @@
                     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=cut><a class=header href=#cut>cut</a></h1><p><code>cut</code> is a handy tool for many field processing use cases. The features are limited compared to say <code>awk</code> or <code>perl</code>, but the reduced scope also leads to faster processing.<h2 id=individual-field-selections><a class=header href=#individual-field-selections>Individual field selections</a></h2><p>You can use the <code>-f</code> option to select one or more fields separated by the comma character. By default, <code>cut</code> splits the input on tab character.<pre><code class=language-bash># second field
+                </script><div id=content class=content><main><div class=sidetoc><nav class=pagetoc></nav></div><h1 id=cut><a class=header href=#cut>cut</a></h1><p><code>cut</code> is a handy tool for many field processing use cases. The features are limited compared to <code>awk</code> and <code>perl</code> commands, but the reduced scope also leads to faster processing.<h2 id=individual-field-selections><a class=header href=#individual-field-selections>Individual field selections</a></h2><p>By default, <code>cut</code> splits the input content into fields based on the tab character. You can use the <code>-f</code> option to select a desired field from each input line. To extract multiple fields, specify the selections separated by the comma character.<pre><code class=language-bash># second field
 $ printf 'apple\tbanana\tcherry\n' | cut -f2
 banana
 
 # first and third field
 $ printf 'apple\tbanana\tcherry\n' | cut -f1,3
 apple   cherry
-</code></pre><p><code>cut</code> will always display the selected fields in the same order as input. Field duplication will be ignored as well.<pre><code class=language-bash># same as: cut -f1,3
+</code></pre><p><code>cut</code> will always display the selected fields in ascending order. Field duplication will be ignored as well.<pre><code class=language-bash># same as: cut -f1,3
 $ printf 'apple\tbanana\tcherry\n' | cut -f3,1
 apple   cherry
 
 # same as: cut -f1,2
 $ printf 'apple\tbanana\tcherry\n' | cut -f1,1,2,1,2,1,1,2
 apple   banana
-</code></pre><p>By default, <code>cut</code> uses the newline character as the line separator for both input and output.<pre><code class=language-bash>$ printf 'good\tfood\ntip\ttap' | cut -f2
+</code></pre><p>By default, <code>cut</code> uses the newline character as the line separator. <code>cut</code> will add a newline character to the output even if the last input line doesn't end with a newline.<pre><code class=language-bash>$ printf 'good\tfood\ntip\ttap' | cut -f2
 food
 tap
 </code></pre><h2 id=field-ranges><a class=header href=#field-ranges>Field ranges</a></h2><p>You can use the <code>-</code> character to specify field ranges. You can skip the starting or ending range, but not both.<pre><code class=language-bash># 2nd, 3rd and 4th fields
@@ -85,7 +85,7 @@
 -f3: command not found
 $ echo 'one;two;three;four' | cut -d';' -f3
 three
-</code></pre><h2 id=output-field-delimiter><a class=header href=#output-field-delimiter>Output field delimiter</a></h2><p>Use the <code>--output-delimiter</code> option to customize the output separator to any string of your choice. The string 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.<pre><code class=language-bash># same as: tr '\t' ','
+</code></pre><h2 id=output-field-delimiter><a class=header href=#output-field-delimiter>Output field delimiter</a></h2><p>Use the <code>--output-delimiter</code> option to customize the output separator to any string of your choice. The string 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.<pre><code class=language-bash># same as: tr '\t' ','
 $ printf 'apple\tbanana\tcherry\n' | cut --output-delimiter=, -f1-
 apple,banana,cherry
 
@@ -111,24 +111,24 @@
 $ printf 'apple ball cat\n1 2 3 4 5' | cut --complement -d' ' -f1,3
 ball
 2 4 5
-</code></pre><h2 id=suppress-lines-without-delimiters><a class=header href=#suppress-lines-without-delimiters>Suppress lines without delimiters</a></h2><p>By default, lines not containing the specified input delimiter will be part of the output. You can use the <code>-s</code> option to suppress such lines.<pre><code class=language-bash>$ printf '1,2,3,4\nhello\na,b,c\n'
+</code></pre><h2 id=suppress-lines-without-delimiters><a class=header href=#suppress-lines-without-delimiters>Suppress lines without delimiters</a></h2><p>By default, lines not containing the input delimiter will still be part of the output. You can use the <code>-s</code> option to suppress such lines.<pre><code class=language-bash>$ cat mixed_fields.csv
 1,2,3,4
 hello
 a,b,c
 
 # second line doesn't have the comma separator
 # by default, such lines will be part of the output
-$ printf '1,2,3,4\nhello\na,b,c\n' | cut -d, -f2
+$ cut -d, -f2 mixed_fields.csv
 2
 hello
 b
 
 # use -s option to suppress such lines
-$ printf '1,2,3,4\nhello\na,b,c\n' | cut -sd, -f2
+$ cut -sd, -f2 mixed_fields.csv
 2
 b
 
-$ printf '1,2,3,4\nhello\na,b,c\n' | cut --complement -sd, -f2
+$ cut --complement -sd, -f2 mixed_fields.csv
 1,3,4
 a,c
 </code></pre><p>If a line contains the specified delimiter but doesn't have the field number requested, you'll get a blank line. The <code>-s</code> option has no effect on such lines.<pre><code class=language-bash>$ printf 'apple ball cat\n1 2 3 4 5' | cut -d' ' -f4

head-tail.html

@@ -77,11 +77,13 @@
 13) Much ado about nothing
 14) He he he
 15) Adios amigo
-</code></pre><p>If there are less than 10 lines in the input, only those lines will be displayed.<pre><code class=language-bash># same as: seq 3 | tail
-$ seq 3 | head
+</code></pre><p>If there are less than 10 lines in the input, only those lines will be displayed.<pre><code class=language-bash># seq command will be discussed in detail later, generates 1 to 4 here
+# same as: seq 4 | tail
+$ seq 4 | head
 1
 2
 3
+4
 </code></pre><p>You can use the <code>-nN</code> option to customize the number of lines (<code>N</code>) needed.<pre><code class=language-bash># first three lines
 # space between -n and N is optional
 $ head -n3 sample.txt
@@ -160,6 +162,6 @@
 
 $ printf 'car\0jeep\0bus\0' | tail -z -n2 | cat -v
 jeep^@bus^@
-</code></pre></main><nav class=nav-wrapper aria-label="Page navigation"><a rel=prev href=cat-tac.html class="mobile-nav-chapters previous"title="Previous chapter"aria-label="Previous chapter"aria-keyshortcuts=Left> <i class="fa fa-angle-left"></i> </a><a rel=next href=tr.html class="mobile-nav-chapters next"title="Next chapter"aria-label="Next chapter"aria-keyshortcuts=Right> <i class="fa fa-angle-right"></i> </a><div style="clear: both"></div></nav></div></div><nav class=nav-wide-wrapper aria-label="Page navigation"><a rel=prev href=cat-tac.html class="nav-chapters previous"title="Previous chapter"aria-label="Previous chapter"aria-keyshortcuts=Left> <i class="fa fa-angle-left"></i> </a><a rel=next href=tr.html class="nav-chapters next"title="Next chapter"aria-label="Next chapter"aria-keyshortcuts=Right> <i class="fa fa-angle-right"></i> </a></nav></div><script>
+</code></pre><h2 id=further-reading><a class=header href=#further-reading>Further Reading</a></h2><ul><li><a href=https://en.wikipedia.org/wiki/Tail_(Unix)#File_monitoring>wikipedia: File monitoring with tail -f and -F options</a><li><a href=https://unix.stackexchange.com/q/18760/109046>unix.stackexchange: How does the tail -f option work?</a><li><a href=https://mywiki.wooledge.org/BashFAQ/009>How to deal with output buffering?</a></ul></main><nav class=nav-wrapper aria-label="Page navigation"><a rel=prev href=cat-tac.html class="mobile-nav-chapters previous"title="Previous chapter"aria-label="Previous chapter"aria-keyshortcuts=Left> <i class="fa fa-angle-left"></i> </a><a rel=next href=tr.html class="mobile-nav-chapters next"title="Next chapter"aria-label="Next chapter"aria-keyshortcuts=Right> <i class="fa fa-angle-right"></i> </a><div style="clear: both"></div></nav></div></div><nav class=nav-wide-wrapper aria-label="Page navigation"><a rel=prev href=cat-tac.html class="nav-chapters previous"title="Previous chapter"aria-label="Previous chapter"aria-keyshortcuts=Left> <i class="fa fa-angle-left"></i> </a><a rel=next href=tr.html class="nav-chapters next"title="Next chapter"aria-label="Next chapter"aria-keyshortcuts=Right> <i class="fa fa-angle-right"></i> </a></nav></div><script>
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paste.html

@@ -55,7 +55,7 @@
 Pink
 Red
 White
-</code></pre><p>By default, <code>paste</code> adds a tab character between corresponding lines of input files. Use <code>-</code> as the filename for <code>stdin</code> data.<pre><code class=language-bash>$ paste colors_1.txt colors_2.txt
+</code></pre><p>By default, <code>paste</code> adds a tab character between corresponding lines of input files.<pre><code class=language-bash>$ paste colors_1.txt colors_2.txt
 Blue    Black
 Brown   Blue
 Orange  Green
@@ -71,13 +71,11 @@
 5,10
 
 # quote the delimiter if it is a shell metacharacter
-$ paste -d'|' <(seq 3) <(seq 4 6) <(seq 7 10)
-1|4|7
-2|5|8
-3|6|9
-||10
-</code></pre><p>Use empty string or <code>\0</code> if you don't want any delimiter between the columns.<pre><code class=language-bash># you can also use paste -d'\0'
-# note that the space between -d and empty string is necessary here
+$ paste -d'|' <(seq 3) <(seq 4 5) <(seq 6 8)
+1|4|6
+2|5|7
+3||8
+</code></pre><p>Use empty string if you don't want any delimiter between the columns. You can also use <code>\0</code> for this case, but that'd be confusing since it is typically used to mean the NUL character.<pre><code class=language-bash># note that the space between -d and empty string is necessary here
 $ paste -d '' <(seq 3) <(seq 6 8)
 16
 27
@@ -107,7 +105,11 @@
 Blue:Brown:Orange
 Purple:Red:Teal
 White::
-</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 (see <a href=https://stackoverflow.com/q/5349718/4082052>this stackoverflow thread</a> for more details).<pre><code class=language-bash># the string before %.s is repeated based on the number of arguments
+</code></pre><p>Here's an example with both <code>stdin</code> and file arguments:<pre><code class=language-bash>$ seq 6 | paste - nums.txt -
+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
 $ printf 'x %.s' a b c
 x x x 
 $ printf -- '- %.s' {1..5}
@@ -116,11 +118,7 @@
 $ seq 10 | paste -d, $(printf -- '- %.s' {1..5})
 1,2,3,4,5
 6,7,8,9,10
-</code></pre><p>Here's an example with both <code>stdin</code> and file arguments:<pre><code class=language-bash>$ seq 6 | paste - nums.txt -
-1       3.14    2
-3       42      4
-5       1000    6
-</code></pre><h2 id=multicharacter-delimiters><a class=header href=#multicharacter-delimiters>Multicharacter delimiters</a></h2><p>The <code>-d</code> option accepts a list of characters (bytes to be precise) to be used one by one between the different columns. If the number of characters is less than the number of separators required, the characters are reused from the beginning and this cycle repeats until all the columns are done. If the number of characters is greater than the number of separators required, the extra characters are simply discarded.<pre><code class=language-bash># , is used between 1st and 2nd column
+</code></pre><blockquote><p><img src=./images/info.svg alt=info> See <a href=https://stackoverflow.com/q/5349718/4082052>this stackoverflow thread</a> for more details about the <code>printf</code> solution and other alternatives.</blockquote><h2 id=multicharacter-delimiters><a class=header href=#multicharacter-delimiters>Multicharacter delimiters</a></h2><p>The <code>-d</code> option accepts a list of characters (bytes to be precise) to be used one by one between the different columns. If the number of characters is less than the number of separators required, the characters are reused from the beginning and this cycle repeats until all the columns are done. If the number of characters is greater than the number of separators required, the extra characters are simply discarded.<pre><code class=language-bash># , is used between 1st and 2nd column
 # - is used between 2nd and 3rd column
 $ paste -d',-' <(seq 3) <(seq 4 6) <(seq 7 9)
 1,4-7

searchindex.js

@@ -55,7 +55,7 @@
 -5
 -4
 -3
-</code></pre><p>When you want to specify all three numbers, the order is start, step and stop.<pre><code class=language-bash># start=1000, step=5 and stop=1010
+</code></pre><p>When you want to specify all the three numbers, the order is start, step and stop.<pre><code class=language-bash># start=1000, step=5 and stop=1010
 $ seq 1000 5 1010
 1000
 1005
@@ -92,7 +92,7 @@
 120.000
 120.752
 121.504
-</code></pre><h2 id=customizing-separator><a class=header href=#customizing-separator>Customizing separator</a></h2><p>You can use the <code>-s</code> option to change the separator between the numbers of a sequence. Multiple characters are allowed. 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 use escapes like <code>\t</code> instead of a literal tab character. A newline is always added at end.<pre><code class=language-bash>$ seq -s' ' 4
+</code></pre><h2 id=customizing-separator><a class=header href=#customizing-separator>Customizing separator</a></h2><p>You can use the <code>-s</code> option to change the separator between the numbers of a sequence. Multiple characters are allowed. 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 use escapes like <code>\t</code> instead of a literal tab character. A newline is always added at the end of the output.<pre><code class=language-bash>$ seq -s' ' 4
 1 2 3 4
 
 $ seq -s: -2 0.75 3
@@ -122,7 +122,7 @@
 0001
 0002
 0003
-</code></pre><h2 id=printf-style-formatting><a class=header href=#printf-style-formatting>printf style formatting</a></h2><p>You can use the <code>-f</code> option for <code>printf</code> style floating-point number formatting.<pre><code class=language-bash>$ seq -f'%g' -s: 1 0.75 3
+</code></pre><h2 id=printf-style-formatting><a class=header href=#printf-style-formatting>printf style formatting</a></h2><p>You can use the <code>-f</code> option for <code>printf</code> style floating-point number formatting. See <a href=https://www.gnu.org/software/bash/manual/html_node/Bash-Builtins.html#index-printf>bash manual: printf</a> for more details on formatting options.<pre><code class=language-bash>$ seq -f'%g' -s: 1 0.75 3
 1:1.75:2.5
 
 $ seq -f'%.4f' -s: 1 0.75 3
@@ -132,12 +132,14 @@
 1.200e+02
 1.208e+02
 1.215e+02
-</code></pre><h2 id=limitations><a class=header href=#limitations>Limitations</a></h2><p>As per <a href=https://www.gnu.org/software/coreutils/manual/html_node/seq-invocation.html#seq-invocation>the manual</a>:<blockquote><p>On most systems, <code>seq</code> can produce whole-number output for values up to at least <code>2^53</code>. Larger integers are approximated. The details differ depending on your floating-point implementation.</blockquote><pre><code class=language-bash>$ seq 100000000000000000000 3 100000000000000000010
+</code></pre><h2 id=limitations><a class=header href=#limitations>Limitations</a></h2><p>As per <a href=https://www.gnu.org/software/coreutils/manual/html_node/seq-invocation.html#seq-invocation>the manual</a>:<blockquote><p>On most systems, <code>seq</code> can produce whole-number output for values up to at least <code>2^53</code>. Larger integers are approximated. The details differ depending on your floating-point implementation.</blockquote><pre><code class=language-bash># example with approximate values
+$ seq 100000000000000000000 3 100000000000000000010
 100000000000000000000
 100000000000000000000
 100000000000000000008
 100000000000000000008
-</code></pre><blockquote><p>However, note that when limited to non-negative whole numbers, an increment of <code>1</code> and no format-specifying option, <code>seq</code> can print arbitrarily large numbers.</blockquote><pre><code class=language-bash>$ seq 100000000000000000000000000000 100000000000000000000000000005
+</code></pre><blockquote><p>However, note that when limited to non-negative whole numbers, an increment of <code>1</code> and no format-specifying option, <code>seq</code> can print arbitrarily large numbers.</blockquote><pre><code class=language-bash># no approximation for step value of 1
+$ seq 100000000000000000000000000000 100000000000000000000000000005
 100000000000000000000000000000
 100000000000000000000000000001
 100000000000000000000000000002