go - Remove first line from text file in Golang -


i'm trying pop first line of file , reduce file lines 1 one. implementation removing first line follows

type fs struct {     ...     file       *os.file }  //file creation ok...   func (fs *fs) pop() []byte {     var buf []string     scanner := bufio.newscanner(fs.file)     //reading lines     scanner.scan() {         line := scanner.text()         buf = append(buf, line)     }     //writing second line on same file     s := 1; s < len(buf); s++ {         fs.file.writestring(fmt.println(buf[s]))     }     //commit changes     fs.file.sync()     fs.file.close()      return []byte(buf[0]) }

i returned []byte expected string file never changes. missing here?

for example,

package main  import (     "bytes"     "fmt"     "io"     "os" )  func popline(f *os.file) ([]byte, error) {     fi, err := f.stat()     if err != nil {         return nil, err     }     buf := bytes.newbuffer(make([]byte, 0, fi.size()))      _, err = f.seek(0, os.seek_set)     if err != nil {         return nil, err     }     _, err = io.copy(buf, f)     if err != nil {         return nil, err     }     line, err := buf.readstring('\n')     if err != nil && err != io.eof {         return nil, err     }      _, err = f.seek(0, os.seek_set)     if err != nil {         return nil, err     }     nw, err := io.copy(f, buf)     if err != nil {         return nil, err     }     err = f.truncate(nw)     if err != nil {         return nil, err     }     err = f.sync()     if err != nil {         return nil, err     }      _, err = f.seek(0, os.seek_set)     if err != nil {         return nil, err     }     return []byte(line), nil }  func main() {     fname := `popline.txt`     f, err := os.openfile(fname, os.o_rdwr|os.o_create, 0666)     if err != nil {         fmt.println(err)         return     }     defer f.close()     line, err := popline(f)     if err != nil {         fmt.println(err)         return     }     fmt.println("pop:", string(line)) } 
 $ cat popline.txt lorem ipsum dolor sit amet, consectetur adipiscing elit,  sed eiusmod tempor incididunt ut labore et dolore magna aliqua.  ut enim ad minim veniam,  quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.  duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.  excepteur sint occaecat cupidatat non proident,  sunt in culpa qui officia deserunt mollit anim id est laborum.  $ go run popline.go pop: lorem ipsum dolor sit amet, consectetur adipiscing elit,   $ cat popline.txt sed eiusmod tempor incididunt ut labore et dolore magna aliqua.  ut enim ad minim veniam,  quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.  duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.  excepteur sint occaecat cupidatat non proident,  sunt in culpa qui officia deserunt mollit anim id est laborum.  $

Comments

Post a Comment

Popular posts from this blog

powershell Start-Process exit code -1073741502 when used with Credential from a windows service environment -

i'm running strange behavior powershell start-process call. here call: $process = start-process ` "c:\somepath\mybinary.exe" ` -passthru ` -credential $defaultcredential ` -wait ` -workingdirectory "c:\somepath" ` -loaduserprofile if ($process.exitcode -ne 0) { #do } this call return exit code - 1073741502 . after quick search, exit code seems related generic error when program not load required dll (aka. status_dll_init_failed ). when run without -credential $credential program runs correctly. in order isolate problem, manually launched some.exe in prompt target credential , runs smoothly. so problem seems come way start-process cmdlet launch process. i found potential solutions problem tried apply no luck : link , link . would have idea of what's going on here ? edit 1: run proc mon monitoring program activities when launched directly or via powershell script. problem seems occur when loading kernelbase
Read more

twig - Using Twigbridge in a Laravel 5.1 Package -

i'm trying create laravel 5.1 package uses twigbridge instead of .php views. can normal .php views display fine, when try make use of .twig templates i'm met error. possible use twigbridge templates when creating views laravel package or pretty stuck blade , php ? edit 1: loading twig template without extending works. it's when start using {% extends 'file' %} error comes out. i error error loading /virtual/laravel/packages/username/mypackage/src/views/sample.twig: template "templates.master" not defined () in "/virtual/laravel/packages/username/mypackage/src/views/sample.twig" @ line 1. my folders username |_ mypackage |_ src |_ controllers - samplecontroller.php |_ views |_ templates - master.twig - sample.twig twig template sample.twig {% extends 'templates.master' %} {% block content %} {{ parent()
Read more

c# - LINQ join Entities from HashSet's, Join vs Dictionary vs HashSet performance -

i have hashset's each stores t, have written test application compares different relation algorithms can think of, i'm not pleased results getting. does there exist more efficient ways of achieving object relations, once testing? using system; using system.collections.generic; using system.linq; using system.text; using system.threading.tasks; using system.diagnostics; namespace linqtests { class program { static void main(string[] args) { hashset<user> usertable = new hashset<user>(); hashset<userproperty> userpropertytable = new hashset<userproperty>(); #region lets create dummy data. console.writeline("please wait while creating dummy data, can take while..."); console.writeline(""); int rows = 1000000; for(int x = 0; x < rows; x++) { random rnd = new random(); // ad
Read more