When I had this requirement at the start, I had very less information to work on.Just a class called

SysAttachment and a method called getBytes(Inherited from the Object class).

I am handling the entire conversion of the entire attachment into an array of strings in the UI action itself. You can use a Script Include and call this Script Include from the UI action if you choose to make this client callable.

Name of the UI Action : AddCI's

//This will only get the CI names from a csv sheet. You can do similar thing for a .txt file.

var gr = new GlideRecord('sys_attachment');gr.addQuery('table_sys_id', current.sys_id);gr.addQuery('file_name','UploadCI.csv');gr.addQuery('content_type','application/vnd.ms-excel');gr.query();if (gr.next()){     var sa = new Packages.com.glide.ui.SysAttachment();     var binData = sa.getBytes(gr);     var string = new Packages.java.lang.String(binData);     gs.log(string);var arr = string.split("\n");     for(i=0; i.toString();         var len = str.length();         var newStr = str.substring(0,len-2);         var grA = new GlideRecord("cmdb_ci");         grA.addQuery("name",'STARTSWITH',newStr);         grA.query();         if(grA.next()){             taskCI.ci_item = grA.sys_id;             taskCI.insert();         }         else {             gs.addInfoMessage(" There is no CI by the name:"+arr);         }     }     action.setRedirectURL(current);}else{     gs.addInfoMessage("You haven't attached any file by the name UploadCI.csv");     action.setRedirectURL(current);