Is it possible to pass a flag to Gulp to have it run tasks in different ways

Question

Normally in Gulp tasks look like this   gulp task  my-task   function         return gulp src options SCSS SOURCE           pipe sass  style  nested              pipe autoprefixer  last 10 version             pipe concat  style css             pipe gulp dest options SCSS DEST          Is it possible to pass a command line flag to gulp  that s not a task  and have it run tasks conditionally based on that  For instance    gulp my-task -a 1   And then in my gulpfile js   gulp task  my-task   function             if  a    1                var source   options SCSS SOURCE            else               var source   options OTHER SOURCE                    return gulp src source               pipe sass  style  nested                  pipe autoprefixer  last 10 version                 pipe concat  style css                 pipe gulp dest options SCSS DEST

User · Answer

If you ve some strict  ordered   arguments  then you can get them simply by checking process argv   var args   process argv slice 2    if  args 0       --env   amp  amp  args 1       production      Execute it  gulp --env production     however  I think that this is tooo strict and not bulletproof  So  I fiddled a bit around    and ended up with this utility function   function getArg key      var index   process argv indexOf key     var next   process argv index   1     return  index  lt  0    null     next    next 0       -     true   next      It eats an argument-name and will search for this in process argv  If nothing was found it spits out null  Otherwise if their is no next argument or the next argument is a command and not a value  we differ with a dash  true gets returned   That s because the key exist  but there s just no value   If all the cases before will fail  the next argument-value is what we get    gt  gulp watch --foo --bar 1337 -boom  Foo isn t equal to bar    getArg  --foo        gt  true getArg  --bar        gt   1337  getArg  -boom        gt   Foo isn t equal to bar   getArg  --404        gt  null   Ok  enough for now    Here s a simple example using gulp   var gulp   require  gulp    var sass   require  gulp-sass    var rename   require  gulp-rename     var env   getArg  --env     gulp task  styles   function        return gulp src    index scss      pipe sass       style  env      production     compressed     nested           pipe rename       extname  env      production      min css      css           pipe gulp dest    build           Run it gulp --env production

User · Answer

And if you are using typescript  gulpfile ts  then do this for yargs  building on  Caio Cunha s excellent answer https   stackoverflow com a 23038290 1019307 and other comments above    Install  npm install --save-dev yargs  typings install dt yargs --global --save    ts files  Add this to the  ts files   import   argv   from  yargs           let debug  boolean   argv debug    This has to be done in each  ts file individually  even the tools tasks project files that are imported into the gulpfile ts js    Run  gulp build dev --debug   Or under npm pass the arg through to gulp   npm run build dev -- --debug

User · Answer

It has been some time since this question has been posted  but maybe it will help someone    I am using GULP CLI 2 0 1  installed globally  and GULP 4 0 0  installed locally  here is how you do it without any additional plugin  I think the code is quite self-explanatory   var cp   require  child process       src  dest  series  parallel  watch     require  gulp           availableTasks  log available tasks to console function availableTasks done      var command    gulp --tasks-simple     if  process argv indexOf  --verbose    gt  -1        command    gulp --tasks         cp exec command  function err  stdout  stderr        done console log  Available tasks are  n    stdout            availableTasks displayName    tasks   availableTasks description    Log available tasks to console as plain text list    availableTasks flags        --verbose    Display tasks dependency tree instead of plain text list      exports availableTasks   availableTasks    And run from the console   gulp availableTasks   Then run and see the differences   gulp availableTasks --verbose

User · Answer

Here s a quick recipe I found   gulpfile js  var gulp     require  gulp        npm install gulp yargs gulp-if gulp-uglify var args     require  yargs   argv  var gulpif   require  gulp-if    var uglify   require  gulp-uglify     var isProduction   args env      production    gulp task  scripts   function       return gulp src       js        pipe gulpif isProduction  uglify        only minify if production      pipe gulp dest  dist           CLI  gulp scripts --env production   Original Ref  not available anymore   https   github com gulpjs gulp blob master docs recipes pass-params-from-cli md    Alternative with minimist  From Updated Ref  https   github com gulpjs gulp blob master docs recipes pass-arguments-from-cli md  gulpfile js     npm install --save-dev gulp gulp-if gulp-uglify minimist  var gulp   require  gulp    var gulpif   require  gulp-if    var uglify   require  gulp-uglify     var minimist   require  minimist     var knownOptions       string   env     default    env  process env NODE ENV     production        var options   minimist process argv slice 2   knownOptions    gulp task  scripts   function       return gulp src       js        pipe gulpif options env      production   uglify        only minify if production      pipe gulp dest  dist           CLI  gulp scripts --env production

User · Answer

var isProduction    process argv indexOf  production   gt -1     CLI gulp production calls my production task and sets a flag for any conditionals

User · Answer

Gulp doesn t offer any kind of util for that  but you can use one of the many command args parsers  I like yargs  Should be   var argv   require  yargs   argv   gulp task  my-task   function         return gulp src argv a    1   options SCSS SOURCE   options OTHER SOURCE           pipe sass  style  nested              pipe autoprefixer  last 10 version             pipe concat  style css             pipe gulp dest options SCSS DEST          You can also combine it with gulp-if to conditionally pipe the stream  very useful for dev vs  prod building   var argv   require  yargs   argv      gulpif   require  gulp-if        rename   require  gulp-rename        uglify   require  gulp-uglify     gulp task  my-js-task   function       gulp src  src      js        pipe concat  out js         pipe gulpif argv production  uglify          pipe gulpif argv production  rename  suffix    min           pipe gulp dest  dist            And call with gulp my-js-task or gulp my-js-task --production

User · Answer

Edit  gulp-util is deprecated and should be avoid  so it s recommended to use minimist instead  which gulp-util already used   So I ve changed some lines in my gulpfile to remove gulp-util   var argv   require  minimist   process argv slice 2     gulp task  styles   function       return gulp src   src styles      argv theme     main       scss                  Original  In my project I use the following flag   gulp styles --theme literature   Gulp offers an object gulp env for that  It s deprecated in newer versions  so you must use gulp-util for that  The tasks looks like this   var util   require  gulp-util     gulp task  styles   function       return gulp src   src styles      util env theme   util env theme    main       scss         pipe compass           config file     config rb           sass      src styles           css       dist styles           style     expanded                pipe autoprefixer  last 2 version    safari 5    ie 8    ie 9    ff 17    opera 12 1    ios 6    android 4         pipe livereload server        pipe gulp dest  dist styles         pipe notify   message   Styles task complete             The environment setting is available during all subtasks  So I can use this flag on the watch task too   gulp watch --theme literature   And my styles task also works   Ciao Ralf

User · Answer

We wanted to pass a different config file for different environments -- one for production  dev and testing  This is the code in the gulp file    x000D   x000D    passing in flag to gulp to set environment x000D    var env   gutil env env  x000D   x000D  if  typeof gutil env env      string     x000D    process env NODE ENV   gutil env env  x000D    x000D   x000D   x000D    This is the code in the app js file    x000D   x000D    if env      testing    x000D        var Config   require    config testing js    x000D        var Api   require    api testing js   Config web   x000D        x000D      else if env      dev    x000D         Config   require    config dev js    x000D          Api   require    api dev js   Api  x000D        x000D      else  x000D         Config   require    config production js    x000D         Api   require    api production js   Config web   x000D        x000D   x000D   x000D    And then to run it gulp --env testing

User · Answer

Pass arguments from the command line     npm install --save-dev gulp gulp-if gulp-uglify minimist  var gulp   require  gulp    var gulpif   require  gulp-if    var uglify   require  gulp-uglify     var minimist   require  minimist     var knownOptions       string   env     default    env  process env NODE ENV     production        var options   minimist process argv slice 2   knownOptions    gulp task  scripts   function       return gulp src       js        pipe gulpif options env      production   uglify        only minify in production      pipe gulp dest  dist           Then run gulp with     gulp scripts --env development   Source

User · Answer

I built a plugin to inject parameters from the commandline into the task callback   gulp task  mytask   function  production      console log production        gt  true         gulp mytask --production   https   github com stoeffel gulp-param  If someone finds a bug or has a improvement to it  I am happy to merge PRs

User · Answer

There s a very simple way to do on off flags without parsing the arguments  gulpfile js is just a file that s executed like any other  so you can do   var flags       production  false     gulp task  production   function        flags production   true        And use something like gulp-if to conditionally execute a step  gulp task  build   function        gulp src    html        pipe gulp if flags production  minify html          pipe gulp dest  build            Executing gulp build will produce a nice html  while gulp production build will minify it

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