{"id":564,"date":"2022-04-21T10:32:00","date_gmt":"2022-04-21T10:32:00","guid":{"rendered":"https:\/\/andrejacobs.org\/?p=564"},"modified":"2022-04-22T10:35:33","modified_gmt":"2022-04-22T10:35:33","slug":"learning-go-day-5","status":"publish","type":"post","link":"https:\/\/andrejacobs.org\/study-notes\/learning-go-day-5\/","title":{"rendered":"Learning Go &#8211; Day 5"},"content":{"rendered":"\n<p class=\"has-small-font-size\">Featured image by\u00a0<a href=\"https:\/\/github.com\/egonelbre\/gophers\" target=\"_blank\" rel=\"noreferrer noopener\">Egon Elbre<\/a><\/p>\n\n\n\n<div class=\"wp-block-jetpack-markdown\"><ul>\n<li>Finishing going through <a href=\"https:\/\/golangbot.com\/learn-golang-series\/\">https:\/\/golangbot.com\/learn-golang-series\/<\/a><\/li>\n<li>Continuing to watch some of <a href=\"https:\/\/www.youtube.com\/watch?v=rFejpH_tAHM&amp;list=PLEcwzBXTPUE9V1o8mZdC9tNnRZaTgI-1P\">Golang University 101<\/a>\n<ul>\n<li><a href=\"https:\/\/www.youtube.com\/watch?v=eMz0vni6PAw&amp;t=7s\">GopherCon 2019: Carolyn Van Slyck &#8211; Design Command-Line Tools People Love<\/a><\/li>\n<li><a href=\"https:\/\/www.youtube.com\/watch?v=f6kdp27TYZs\">Google I\/O 2012 &#8211; Go Concurrency Patterns<\/a><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h3>Reading files<\/h3>\n<ul>\n<li>Reading the entire file into memory.<\/li>\n<\/ul>\n<pre><code class=\"language-go\">import &quot;io\/ioutil&quot;\n\ndata, err := ioutil.ReadFile(&quot;lorem.txt&quot;)\nif err != nil {\n\tfmt.Println(&quot;Failed to read the file. Error: &quot;, err)\n\treturn\n}\n\/\/NOTE: ReadFile returns a byte slice\nfmt.Printf(&quot;Contents of file:\\n%s\\n&quot;, string(data))\n<\/code><\/pre>\n<ul>\n<li>You can pack static files into the binary using a tool like <a href=\"https:\/\/github.com\/gobuffalo\/packr\/\">packr<\/a>. Might and might not be of use to me in the future.<\/li>\n<li>Reading a file in chunks using <code>bufio<\/code> package.<\/li>\n<\/ul>\n<pre><code class=\"language-go\">package main\n\nimport (\n\t&quot;bufio&quot;\n\t&quot;fmt&quot;\n\t&quot;log&quot;\n\t&quot;os&quot;\n)\n\nfunc main() {\n\t\/\/ Open the file\n\tf, err := os.Open(&quot;lorem.txt&quot;)\n\tif err != nil {\n\t\tlog.Fatal(err)\n\t}\n\n\t\/\/ Ensure the file is closed when we are done\n\tdefer func() {\n\t\tif err = f.Close(); err != nil {\n\t\t\tlog.Fatal(err)\n\t\t}\n\t}()\n\n\t\/\/ Read from the file (f) into a buffer (b) 128 bytes at a time\n\tr := bufio.NewReader(f)\n\tb := make([]byte, 128)\n\tfor {\n\t\tn, err := r.Read(b)\n\t\tif err != nil {\n\t\t\tfmt.Println(&quot;Error reading file:&quot;, err)\n\t\t\tbreak\n\t\t}\n\t\tfmt.Println(string(b[0:n]))\n\t}\n}\n<\/code><\/pre>\n<ul>\n<li>Reading a text file line by line.<\/li>\n<\/ul>\n<pre><code class=\"language-go\">s := bufio.NewScanner(f)\nfor s.Scan() {\n    fmt.Println(s.Text())\n}\n\/\/ Check if any errors occurred (other than EOF)\nerr = s.Err()\nif err != nil {\n    log.Fatal(err)\n}\n<\/code><\/pre>\n<h3>Writing files<\/h3>\n<ul>\n<li>Writing strings to a file.<\/li>\n<\/ul>\n<pre><code class=\"language-go\">package main\n\nimport (\n\t&quot;fmt&quot;\n\t&quot;log&quot;\n\t&quot;os&quot;\n)\n\nfunc main() {\n\t\/\/ Create a new file\n\tf, err := os.Create(&quot;test.txt&quot;)\n\tif err != nil {\n\t\tlog.Fatal(err)\n\t\treturn\n\t}\n\n\t\/\/ Ensure the file is closed when we are done\n\tdefer func() {\n\t\tif err = f.Close(); err != nil {\n\t\t\tlog.Fatal(err)\n\t\t}\n\t}()\n\n  \/\/ Write a single string\n\tbc, err := f.WriteString(&quot;The quick brown fox ...&quot;)\n\tif err != nil {\n\t\tlog.Fatal(err)\n\t\treturn\n\t}\n\n\tfmt.Println(bc, &quot;bytes written successfully&quot;)\n}\n<\/code><\/pre>\n<ul>\n<li>Writing bytes to file.<\/li>\n<\/ul>\n<pre><code class=\"language-go\">data := []byte{0x41, 0x6E, 0x64, 0x72, 0x65}\nbc, err := f.Write(data)\n<\/code><\/pre>\n<ul>\n<li>The <code>fmt<\/code> package also have some nice utility functions like <code>FPrintf<\/code> &amp; <code>FPrintln<\/code><\/li>\n<li>Open a file for appending.<\/li>\n<\/ul>\n<pre><code class=\"language-go\">f, err := os.OpenFile(&quot;\/path\/to\/file&quot;, os.O_APPEND | os.O_WRONLY, 0644)\n\/\/ Flags are append and &quot;write-only&quot;\n\/\/ Also passing unix permissions 0644\n<\/code><\/pre>\n<h3>What\u2019s next?<\/h3>\n<p>I will be working through Alex Ellis\u2019 <a href=\"https:\/\/openfaas.gumroad.com\/l\/everyday-golang\">Everyday Golang<\/a> book.<\/p>\n<p>I already know of at least 2 small little programs that I want to write that deals with my Linux server and to help me organise some of my data. More details will follow once I actually write the apps.<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Featured image by\u00a0Egon Elbre [&#8230;]<\/p>\n<p><a class=\"understrap-read-more-link\" href=\"https:\/\/andrejacobs.org\/study-notes\/learning-go-day-5\/\">Read more &rarr;<\/a><\/p>\n","protected":false},"author":2,"featured_media":550,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_mi_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[52],"tags":[53],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v19.13 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Learning Go - Day 5 - Andr\u00e9 Jacobs<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/andrejacobs.org\/study-notes\/learning-go-day-5\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Learning Go - Day 5 - Andr\u00e9 Jacobs\" \/>\n<meta property=\"og:description\" content=\"Featured image by\u00a0Egon Elbre [...]Read more &rarr;\" \/>\n<meta property=\"og:url\" content=\"https:\/\/andrejacobs.org\/study-notes\/learning-go-day-5\/\" \/>\n<meta property=\"og:site_name\" content=\"Andr\u00e9 Jacobs\" \/>\n<meta property=\"article:published_time\" content=\"2022-04-21T10:32:00+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2022-04-22T10:35:33+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/andrejacobs.org\/wp-content\/uploads\/2022\/04\/pirate-boat.png\" \/>\n\t<meta property=\"og:image:width\" content=\"822\" \/>\n\t<meta property=\"og:image:height\" content=\"905\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"author\" content=\"Andr\u00e9 Jacobs\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@andrejacobs81\" \/>\n<meta name=\"twitter:site\" content=\"@andrejacobs81\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Andr\u00e9 Jacobs\" \/>\n\t<meta name=\"twitter:label2\" content=\"Estimated reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"2 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/andrejacobs.org\/study-notes\/learning-go-day-5\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/andrejacobs.org\/study-notes\/learning-go-day-5\/\"},\"author\":{\"name\":\"Andr\u00e9 Jacobs\",\"@id\":\"https:\/\/andrejacobs.org\/#\/schema\/person\/3d38360883015e883c80c2fb875c5a68\"},\"headline\":\"Learning Go &#8211; 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