Get offset/position of bytes written to file
2
I'm writing a string to a file, and I'd like to get the offset of the string which was just written.
Here is the code writing the file:
package main
import (
"os"
)
func main() {
path := "test_file.txt"
byteString := byte("string to write")
f, err := os.OpenFile(path, os.O_APPEND|os.O_WRONLY, 0600)
if err != nil {
panic(err)
}
defer f.Close()
if _, err = f.Write(byteString); err != nil {
panic(err)
}
}
How can I get the offset after having written the line ?
go
asked Nov 24 '18 at 10:00
Graham SlickGraham Slick
2,84142755
add a comment |
2
I'm writing a string to a file, and I'd like to get the offset of the string which was just written.
Here is the code writing the file:
package main
import (
"os"
)
func main() {
path := "test_file.txt"
byteString := byte("string to write")
f, err := os.OpenFile(path, os.O_APPEND|os.O_WRONLY, 0600)
if err != nil {
panic(err)
}
defer f.Close()
if _, err = f.Write(byteString); err != nil {
panic(err)
}
}
How can I get the offset after having written the line ?
go
asked Nov 24 '18 at 10:00
Graham SlickGraham Slick
2,84142755
Maybef.Seek(0, os.SEEK_CUR) - len(byteString)
– Mark Plotnick
Nov 24 '18 at 10:49
add a comment |
2
2
2
1
I'm writing a string to a file, and I'd like to get the offset of the string which was just written.
Here is the code writing the file:
package main
import (
"os"
)
func main() {
path := "test_file.txt"
byteString := byte("string to write")
f, err := os.OpenFile(path, os.O_APPEND|os.O_WRONLY, 0600)
if err != nil {
panic(err)
}
defer f.Close()
if _, err = f.Write(byteString); err != nil {
panic(err)
}
}
How can I get the offset after having written the line ?
go
asked Nov 24 '18 at 10:00
Graham SlickGraham Slick
2,84142755
I'm writing a string to a file, and I'd like to get the offset of the string which was just written.
Here is the code writing the file:
package main
import (
"os"
)
func main() {
path := "test_file.txt"
byteString := byte("string to write")
f, err := os.OpenFile(path, os.O_APPEND|os.O_WRONLY, 0600)
if err != nil {
panic(err)
}
defer f.Close()
if _, err = f.Write(byteString); err != nil {
panic(err)
}
}
How can I get the offset after having written the line ?
go
go
asked Nov 24 '18 at 10:00
Graham SlickGraham Slick
2,84142755
asked Nov 24 '18 at 10:00
Graham SlickGraham Slick
2,84142755
asked Nov 24 '18 at 10:00
Graham SlickGraham Slick
2,84142755
asked Nov 24 '18 at 10:00
Graham SlickGraham Slick
2,84142755
asked Nov 24 '18 at 10:00
Graham SlickGraham Slick
2,84142755
2,84142755
Maybef.Seek(0, os.SEEK_CUR) - len(byteString)
– Mark Plotnick
Nov 24 '18 at 10:49
add a comment |
Maybef.Seek(0, os.SEEK_CUR) - len(byteString)
– Mark Plotnick
Nov 24 '18 at 10:49
Maybe
f.Seek(0, os.SEEK_CUR) - len(byteString)– Mark Plotnick
Nov 24 '18 at 10:49
Maybe
f.Seek(0, os.SEEK_CUR) - len(byteString)– Mark Plotnick
Nov 24 '18 at 10:49
add a comment |
1 Answer
1
active
oldest
votes
1
os.Write only returns the length of the bytes written. If you want the offset, you can either:
- Call
os.Statbefore writing, and then useos.WriteAtto write at the offset for the end of the file provided by theFileInfostructure. - Call
os.Statafter writing, and subtract the length written to the file from the new size.
answered Nov 24 '18 at 10:15
Raghav SoodRaghav Sood
72.3k19159173
I've used the second option, works like a charm thanks. However, would you recommend any of your solution over the other ? If yes, why ?
– Graham Slick
Nov 24 '18 at 10:39
add a comment |
Your Answer
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1 Answer
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active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
1
os.Write only returns the length of the bytes written. If you want the offset, you can either:
- Call
os.Statbefore writing, and then useos.WriteAtto write at the offset for the end of the file provided by theFileInfostructure. - Call
os.Statafter writing, and subtract the length written to the file from the new size.
answered Nov 24 '18 at 10:15
Raghav SoodRaghav Sood
72.3k19159173
I've used the second option, works like a charm thanks. However, would you recommend any of your solution over the other ? If yes, why ?
– Graham Slick
Nov 24 '18 at 10:39
add a comment |
1
os.Write only returns the length of the bytes written. If you want the offset, you can either:
- Call
os.Statbefore writing, and then useos.WriteAtto write at the offset for the end of the file provided by theFileInfostructure. - Call
os.Statafter writing, and subtract the length written to the file from the new size.
answered Nov 24 '18 at 10:15
Raghav SoodRaghav Sood
72.3k19159173
I've used the second option, works like a charm thanks. However, would you recommend any of your solution over the other ? If yes, why ?
– Graham Slick
Nov 24 '18 at 10:39
add a comment |
1
1
1
os.Write only returns the length of the bytes written. If you want the offset, you can either:
- Call
os.Statbefore writing, and then useos.WriteAtto write at the offset for the end of the file provided by theFileInfostructure. - Call
os.Statafter writing, and subtract the length written to the file from the new size.
answered Nov 24 '18 at 10:15
Raghav SoodRaghav Sood
72.3k19159173
os.Write only returns the length of the bytes written. If you want the offset, you can either:
- Call
os.Statbefore writing, and then useos.WriteAtto write at the offset for the end of the file provided by theFileInfostructure. - Call
os.Statafter writing, and subtract the length written to the file from the new size.
answered Nov 24 '18 at 10:15
Raghav SoodRaghav Sood
72.3k19159173
answered Nov 24 '18 at 10:15
Raghav SoodRaghav Sood
72.3k19159173
answered Nov 24 '18 at 10:15
Raghav SoodRaghav Sood
72.3k19159173
answered Nov 24 '18 at 10:15
Raghav SoodRaghav Sood
72.3k19159173
72.3k19159173
I've used the second option, works like a charm thanks. However, would you recommend any of your solution over the other ? If yes, why ?
– Graham Slick
Nov 24 '18 at 10:39
add a comment |
I've used the second option, works like a charm thanks. However, would you recommend any of your solution over the other ? If yes, why ?
– Graham Slick
Nov 24 '18 at 10:39
I've used the second option, works like a charm thanks. However, would you recommend any of your solution over the other ? If yes, why ?
– Graham Slick
Nov 24 '18 at 10:39
I've used the second option, works like a charm thanks. However, would you recommend any of your solution over the other ? If yes, why ?
– Graham Slick
Nov 24 '18 at 10:39
add a comment |
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Maybe
f.Seek(0, os.SEEK_CUR) - len(byteString)– Mark Plotnick
Nov 24 '18 at 10:49