added examples for head and tail commands

Author: learnbyexample

404.html

@@ -32,7 +32,7 @@
             }
             html.classList.remove('sidebar-visible');
             html.classList.add("sidebar-" + sidebar);
-        </script><nav id=sidebar class=sidebar aria-label="Table of contents"><div class=sidebar-scrollbox><ol class=chapter><li class="chapter-item expanded affix"><a href=preface.html>Preface</a><li class="chapter-item expanded"><a href=cat-tac.html><strong aria-hidden=true>1.</strong> cat and tac</a></li><br><hr><li class="chapter-item expanded"><i id=git-repository-button class="fa fa-github"></i><a href=https://github.com/learnbyexample/cli_text_processing_coreutils>   Source code</a><li class="chapter-item expanded"><i id=home-button class="fa fa-home"></i><a href=https://learnbyexample.github.io/>   My Blog</a><li class="chapter-item expanded"><i id=book-button class="fa fa-book"></i><a href=https://learnbyexample.github.io/books/>   My Books</a></ol></div><div id=sidebar-resize-handle class=sidebar-resize-handle></div></nav><div id=page-wrapper class=page-wrapper><div class=page><div id=menu-bar-hover-placeholder></div><div id=menu-bar class="menu-bar sticky bordered"><div class=left-buttons><button id=sidebar-toggle class=icon-button type=button title="Toggle Table of Contents"aria-label="Toggle Table of Contents"aria-controls=sidebar><i class="fa fa-bars"></i></button><button id=theme-toggle class=icon-button type=button title="Change theme"aria-label="Change theme"aria-haspopup=true aria-expanded=false aria-controls=theme-list><i class="fa fa-paint-brush"></i></button><ul id=theme-list class=theme-popup aria-label=Themes role=menu><li role=none><button role=menuitem class=theme id=light>Light (default)</button><li role=none><button role=menuitem class=theme id=rust>Rust</button><li role=none><button role=menuitem class=theme id=coal>Coal</button><li role=none><button role=menuitem class=theme id=navy>Navy</button><li role=none><button role=menuitem class=theme id=ayu>Ayu</button></ul><button id=search-toggle class=icon-button type=button title="Search. (Shortkey: s)"aria-label="Toggle Searchbar"aria-expanded=false aria-keyshortcuts=S aria-controls=searchbar><i class="fa fa-search"></i></button></div><h1 class=menu-title>Command line text processing with GNU Coreutils</h1><div class=right-buttons><a href=https://learnbyexample.github.io title=Blog aria-label=Blog> <i id=home-button class="fa fa-home"></i> </a><a href=https://github.com/learnbyexample/cli_text_processing_coreutils title="Git repository"aria-label="Git repository"> <i id=git-repository-button class="fa fa-github"></i> </a></div></div><div id=search-wrapper class=hidden><form id=searchbar-outer class=searchbar-outer><input type=search id=searchbar name=searchbar placeholder="Search this book ..."aria-controls=searchresults-outer aria-describedby=searchresults-header></form><div id=searchresults-outer class="searchresults-outer hidden"><div id=searchresults-header class=searchresults-header></div><ul id=searchresults></ul></div></div><script>
+        </script><nav id=sidebar class=sidebar aria-label="Table of contents"><div class=sidebar-scrollbox><ol class=chapter><li class="chapter-item expanded affix"><a href=preface.html>Preface</a><li class="chapter-item expanded"><a href=cat-tac.html><strong aria-hidden=true>1.</strong> cat and tac</a><li class="chapter-item expanded"><a href=head-tail.html><strong aria-hidden=true>2.</strong> head and tail</a></li><br><hr><li class="chapter-item expanded"><i id=git-repository-button class="fa fa-github"></i><a href=https://github.com/learnbyexample/cli_text_processing_coreutils>   Source code</a><li class="chapter-item expanded"><i id=home-button class="fa fa-home"></i><a href=https://learnbyexample.github.io/>   My Blog</a><li class="chapter-item expanded"><i id=book-button class="fa fa-book"></i><a href=https://learnbyexample.github.io/books/>   My Books</a></ol></div><div id=sidebar-resize-handle class=sidebar-resize-handle></div></nav><div id=page-wrapper class=page-wrapper><div class=page><div id=menu-bar-hover-placeholder></div><div id=menu-bar class="menu-bar sticky bordered"><div class=left-buttons><button id=sidebar-toggle class=icon-button type=button title="Toggle Table of Contents"aria-label="Toggle Table of Contents"aria-controls=sidebar><i class="fa fa-bars"></i></button><button id=theme-toggle class=icon-button type=button title="Change theme"aria-label="Change theme"aria-haspopup=true aria-expanded=false aria-controls=theme-list><i class="fa fa-paint-brush"></i></button><ul id=theme-list class=theme-popup aria-label=Themes role=menu><li role=none><button role=menuitem class=theme id=light>Light (default)</button><li role=none><button role=menuitem class=theme id=rust>Rust</button><li role=none><button role=menuitem class=theme id=coal>Coal</button><li role=none><button role=menuitem class=theme id=navy>Navy</button><li role=none><button role=menuitem class=theme id=ayu>Ayu</button></ul><button id=search-toggle class=icon-button type=button title="Search. (Shortkey: s)"aria-label="Toggle Searchbar"aria-expanded=false aria-keyshortcuts=S aria-controls=searchbar><i class="fa fa-search"></i></button></div><h1 class=menu-title>Command line text processing with GNU Coreutils</h1><div class=right-buttons><a href=https://learnbyexample.github.io title=Blog aria-label=Blog> <i id=home-button class="fa fa-home"></i> </a><a href=https://github.com/learnbyexample/cli_text_processing_coreutils title="Git repository"aria-label="Git repository"> <i id=git-repository-button class="fa fa-github"></i> </a></div></div><div id=search-wrapper class=hidden><form id=searchbar-outer class=searchbar-outer><input type=search id=searchbar name=searchbar placeholder="Search this book ..."aria-controls=searchresults-outer aria-describedby=searchresults-header></form><div id=searchresults-outer class="searchresults-outer hidden"><div id=searchresults-header class=searchresults-header></div><ul id=searchresults></ul></div></div><script>
                     document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
                     document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
                     Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {

cat-tac.html

@@ -32,7 +32,7 @@
             }
             html.classList.remove('sidebar-visible');
             html.classList.add("sidebar-" + sidebar);
-        </script><nav id=sidebar class=sidebar aria-label="Table of contents"><div class=sidebar-scrollbox><ol class=chapter><li class="chapter-item expanded affix"><a href=preface.html>Preface</a><li class="chapter-item expanded"><a href=cat-tac.html class=active><strong aria-hidden=true>1.</strong> cat and tac</a></li><br><hr><li class="chapter-item expanded"><i id=git-repository-button class="fa fa-github"></i><a href=https://github.com/learnbyexample/cli_text_processing_coreutils>   Source code</a><li class="chapter-item expanded"><i id=home-button class="fa fa-home"></i><a href=https://learnbyexample.github.io/>   My Blog</a><li class="chapter-item expanded"><i id=book-button class="fa fa-book"></i><a href=https://learnbyexample.github.io/books/>   My Books</a></ol></div><div id=sidebar-resize-handle class=sidebar-resize-handle></div></nav><div id=page-wrapper class=page-wrapper><div class=page><div id=menu-bar-hover-placeholder></div><div id=menu-bar class="menu-bar sticky bordered"><div class=left-buttons><button id=sidebar-toggle class=icon-button type=button title="Toggle Table of Contents"aria-label="Toggle Table of Contents"aria-controls=sidebar><i class="fa fa-bars"></i></button><button id=theme-toggle class=icon-button type=button title="Change theme"aria-label="Change theme"aria-haspopup=true aria-expanded=false aria-controls=theme-list><i class="fa fa-paint-brush"></i></button><ul id=theme-list class=theme-popup aria-label=Themes role=menu><li role=none><button role=menuitem class=theme id=light>Light (default)</button><li role=none><button role=menuitem class=theme id=rust>Rust</button><li role=none><button role=menuitem class=theme id=coal>Coal</button><li role=none><button role=menuitem class=theme id=navy>Navy</button><li role=none><button role=menuitem class=theme id=ayu>Ayu</button></ul><button id=search-toggle class=icon-button type=button title="Search. (Shortkey: s)"aria-label="Toggle Searchbar"aria-expanded=false aria-keyshortcuts=S aria-controls=searchbar><i class="fa fa-search"></i></button></div><h1 class=menu-title>Command line text processing with GNU Coreutils</h1><div class=right-buttons><a href=https://learnbyexample.github.io title=Blog aria-label=Blog> <i id=home-button class="fa fa-home"></i> </a><a href=https://github.com/learnbyexample/cli_text_processing_coreutils title="Git repository"aria-label="Git repository"> <i id=git-repository-button class="fa fa-github"></i> </a></div></div><div id=search-wrapper class=hidden><form id=searchbar-outer class=searchbar-outer><input type=search id=searchbar name=searchbar placeholder="Search this book ..."aria-controls=searchresults-outer aria-describedby=searchresults-header></form><div id=searchresults-outer class="searchresults-outer hidden"><div id=searchresults-header class=searchresults-header></div><ul id=searchresults></ul></div></div><script>
+        </script><nav id=sidebar class=sidebar aria-label="Table of contents"><div class=sidebar-scrollbox><ol class=chapter><li class="chapter-item expanded affix"><a href=preface.html>Preface</a><li class="chapter-item expanded"><a href=cat-tac.html class=active><strong aria-hidden=true>1.</strong> cat and tac</a><li class="chapter-item expanded"><a href=head-tail.html><strong aria-hidden=true>2.</strong> head and tail</a></li><br><hr><li class="chapter-item expanded"><i id=git-repository-button class="fa fa-github"></i><a href=https://github.com/learnbyexample/cli_text_processing_coreutils>   Source code</a><li class="chapter-item expanded"><i id=home-button class="fa fa-home"></i><a href=https://learnbyexample.github.io/>   My Blog</a><li class="chapter-item expanded"><i id=book-button class="fa fa-book"></i><a href=https://learnbyexample.github.io/books/>   My Books</a></ol></div><div id=sidebar-resize-handle class=sidebar-resize-handle></div></nav><div id=page-wrapper class=page-wrapper><div class=page><div id=menu-bar-hover-placeholder></div><div id=menu-bar class="menu-bar sticky bordered"><div class=left-buttons><button id=sidebar-toggle class=icon-button type=button title="Toggle Table of Contents"aria-label="Toggle Table of Contents"aria-controls=sidebar><i class="fa fa-bars"></i></button><button id=theme-toggle class=icon-button type=button title="Change theme"aria-label="Change theme"aria-haspopup=true aria-expanded=false aria-controls=theme-list><i class="fa fa-paint-brush"></i></button><ul id=theme-list class=theme-popup aria-label=Themes role=menu><li role=none><button role=menuitem class=theme id=light>Light (default)</button><li role=none><button role=menuitem class=theme id=rust>Rust</button><li role=none><button role=menuitem class=theme id=coal>Coal</button><li role=none><button role=menuitem class=theme id=navy>Navy</button><li role=none><button role=menuitem class=theme id=ayu>Ayu</button></ul><button id=search-toggle class=icon-button type=button title="Search. (Shortkey: s)"aria-label="Toggle Searchbar"aria-expanded=false aria-keyshortcuts=S aria-controls=searchbar><i class="fa fa-search"></i></button></div><h1 class=menu-title>Command line text processing with GNU Coreutils</h1><div class=right-buttons><a href=https://learnbyexample.github.io title=Blog aria-label=Blog> <i id=home-button class="fa fa-home"></i> </a><a href=https://github.com/learnbyexample/cli_text_processing_coreutils title="Git repository"aria-label="Git repository"> <i id=git-repository-button class="fa fa-github"></i> </a></div></div><div id=search-wrapper class=hidden><form id=searchbar-outer class=searchbar-outer><input type=search id=searchbar name=searchbar placeholder="Search this book ..."aria-controls=searchresults-outer aria-describedby=searchresults-header></form><div id=searchresults-outer class="searchresults-outer hidden"><div id=searchresults-header class=searchresults-header></div><ul id=searchresults></ul></div></div><script>
                     document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
                     document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
                     Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
@@ -48,7 +48,7 @@
 </code></pre><p><strong>Here Documents</strong> is another popular way to create such files. Especially inside shell scripts, since pressing <code>Ctrl+d</code> interactively won't be possible. Here's an example:<pre><code class=language-bash># > and a space at the start of lines are only present in interactive mode
 # won't be needed in a shell script
 # EOF is typically used as the identifier
-$  cat << 'EOF' > fruits.txt
+$ cat << 'EOF' > fruits.txt
 > banana
 > papaya
 > mango
@@ -58,7 +58,14 @@
 banana
 papaya
 mango
-</code></pre><p>The termination string is enclosed in single quotes to prevent parameter expansion, command substitution, etc. You can also use <code>\string</code> for this purpose. If you use <code><&LT-</code> instead of <code><<</code>, you can use leading tab characters for indentation purposes. See <a href=https://www.gnu.org/software/bash/manual/bash.html#Here-Documents>bash manual: Here Documents</a> and <a href=https://stackoverflow.com/q/2953081/4082052>stackoverflow: here-documents</a> for more details.<h2 id=concatenate-files><a class=header href=#concatenate-files>Concatenate files</a></h2><p>Here's some examples to showcase <code>cat</code>'s main utility. One or more files can be given as arguments.<pre><code class=language-bash>$ cat greeting.txt fruits.txt nums.txt
+</code></pre><p>The termination string is enclosed in single quotes to prevent parameter expansion, command substitution, etc. You can also use <code>\string</code> for this purpose. If you use <code><&LT-</code> instead of <code><<</code>, you can use leading tab characters for indentation purposes. See <a href=https://www.gnu.org/software/bash/manual/bash.html#Here-Documents>bash manual: Here Documents</a> and <a href=https://stackoverflow.com/q/2953081/4082052>stackoverflow: here-documents</a> for more details.<blockquote><p><img src=./images/info.svg alt=info> Note that creating files as shown above isn't restricted to <code>cat</code>, it can be applied to any command waiting for <code>stdin</code>.</blockquote><pre><code class=language-bash>$ tr 'a-z' 'A-Z' << 'end' > op.txt
+> hi there
+> have a nice day
+> end
+$ cat op.txt
+HI THERE
+HAVE A NICE DAY
+</code></pre><h2 id=concatenate-files><a class=header href=#concatenate-files>Concatenate files</a></h2><p>Here's some examples to showcase <code>cat</code>'s main utility. One or more files can be given as arguments.<pre><code class=language-bash>$ cat greeting.txt fruits.txt nums.txt
 Hi there
 Have a nice day
 banana
@@ -142,7 +149,7 @@
 1 2     3^L4^K5
 </code></pre><p>The <code>-v</code> option doesn't cover the newline and tab characters. You can use the <code>-T</code> option to spot tab characters.<pre><code class=language-bash>$ printf 'good food\tnice dice\n' | cat -T
 good food^Inice dice
-</code></pre><p>The <code>-E</code> option adds a <code>$</code> marker after the final character of input lines.<pre><code class=language-bash>$ printf 'ice   \nwater\n cool  \n' | cat -E
+</code></pre><p>The <code>-E</code> option adds a <code>$</code> marker at the end of input lines. This is useful to spot invisible trailing characters.<pre><code class=language-bash>$ printf 'ice   \nwater\n cool  \n' | cat -E
 ice   $
 water$
  cool  $
@@ -221,6 +228,6 @@
 # you can also use -s '' instead of -s $'\0'
 $ printf 'car\0jeep\0bus\0' | tac -s $'\0' | cat -e
 bus^@jeep^@car^@
-</code></pre><blockquote><p><img src=./images/info.svg alt=info> Use the <code>rev</code> command if you want each input line to be reversed character wise.</blockquote></main><nav class=nav-wrapper aria-label="Page navigation"><a rel=prev href=preface.html class="mobile-nav-chapters previous"title="Previous chapter"aria-label="Previous chapter"aria-keyshortcuts=Left> <i class="fa fa-angle-left"></i> </a><div style="clear: both"></div></nav></div></div><nav class=nav-wide-wrapper aria-label="Page navigation"><a rel=prev href=preface.html class="nav-chapters previous"title="Previous chapter"aria-label="Previous chapter"aria-keyshortcuts=Left> <i class="fa fa-angle-left"></i> </a></nav></div><script>
+</code></pre><blockquote><p><img src=./images/info.svg alt=info> Use the <code>rev</code> command if you want each input line to be reversed character wise.</blockquote></main><nav class=nav-wrapper aria-label="Page navigation"><a rel=prev href=preface.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=head-tail.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=preface.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=head-tail.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>
             window.playground_copyable = true;
         </script><script src=elasticlunr.min.js charset=utf-8></script><script src=mark.min.js charset=utf-8></script><script src=searcher.js charset=utf-8></script><script src=clipboard.min.js charset=utf-8></script><script src=highlight.js charset=utf-8></script><script src=book.js charset=utf-8></script><script src=sidebar.js></script>