digitalmars.D.learn - D Snippet: Reading a file to standard output on Windows Operating
- BoQsc (44/44) Dec 06 2023 It took me a few minutes to get this one right, so that's the
It took me a few minutes to get this one right, so that's the
reason I'm sharing as a thread on the forum.
This snippet opens `example.txt` file and reads it line by line.
Using writeln it prints to the standard output stream.
It also have ability to find a matching line. (if statement)
Additions:
`|` character was used to see the lines more clearly in the
output.
`\r` is important to include in the `if` statement as every line
includes newline character.
**./example.txt** - the input file.
```
test
s
HelloWorld
t
ff
```
**FileScan.d** - Program.
```
import std;
void main(){
foreach (line; File("example.txt").byLine){
writeln("|"~line);
if (line == " HelloWorld\r") { writeln("^This Line is
here."); }
}
}
```
`rdmd FileScan.d`
```
C:\Users\Windows10\Documents\DSearchAndReplace>rdmd FileScan.d
|test
| s
|
| HelloWorld
^This Line is here.
|t
|ff
```
Dec 06 2023
As of recent observation the `line` in the previous
implementation seem to recognise **\r** as default terminator.
Making `writeln("|" ~ line ~ "|");` not possible.
By correcting terminator and disabling it on `byLine` function it
is possible to achieve following output to standard stream:
**Output**
```
|test|
| s|
| |
| HelloWorld|
^This Line is here.
|t|
|ff|
```
**Input (example.txt)**
```
test
s
HelloWorld
t
ff
```
**Source code**
```
import std;
void main(){
foreach (line; File("example.txt").byLine(No.keepTerminator,
"\r\n")){
writeln("|"~line~"|");
if (line == " HelloWorld") { writeln("^This Line is here."); }
}
}
```
Dec 06 2023
On Wednesday, 6 December 2023 at 14:56:50 UTC, BoQsc wrote:
As of recent observation the `line` in the previous
implementation seem to recognise **\r** as default terminator.
Making `writeln("|" ~ line ~ "|");` not possible.
By correcting terminator and disabling it on `byLine` function
it is possible to achieve following output to standard stream:
**Output**
```
|test|
| s|
| |
| HelloWorld|
^This Line is here.
|t|
|ff|
```
**Input (example.txt)**
```
test
s
HelloWorld
t
ff
```
**Source code**
```
import std;
void main(){
foreach (line; File("example.txt").byLine(No.keepTerminator,
"\r\n")){
writeln("|"~line~"|");
if (line == " HelloWorld") { writeln("^This Line is
here."); }
}
}
```
[`strip();`](https://dlang.org/library/std/string/strip.html) can
be used to achieve same result as `No.keepTerminator, "\r\n"` of
`.byLine`
```
import std;
void main(){
foreach (line; File("example.txt").byLine()){
writeln("|" ~ strip(line) ~ "|");
if (line == " HelloWorld") { writeln("^This Line is here."); }
}
}
```
Dec 08 2023
BoQsc <vaidas.boqsc gmail.com>
While outputing to the standard stream, it is also possible to
use `switch` statement to **match a text line to a text line in a
file.** I personally think it improve readability and
maintainability in some applications.
```
import std;
void main(){
foreach (line; File("example.txt").byLine(No.keepTerminator,
"\r\n")){
switch(line) {
case " HelloWorld" :
writeln("|"~line~"|");
writeln("^This Line is here.");
break;
default :
writeln("|"~line~"|");
}
}
}
```
to both: to a standard stream and another file; line by line
In this snippet, we are not only reading a file, editing its
output and outputting to the standard output stream, but also try
to save changes on another file: filling it with the edited
output.
```
import std;
void main(){
File edit = File("example2.txt", "w");
foreach (line; File("example.txt").byLine(No.keepTerminator,
"\r\n")){
switch(line) {
case " HelloWorld":
edit.write("RandomWord\n");
writeln("|"~"RandomWord"~"|");
break;
default :
edit.write(line ~ "\n");
writeln("|" ~ line ~ "|");
}
}
edit.close;
}
```
**Inputs:**
**Example.txt**
```
test
s
HelloWorld
t
ff
```
**Outputs:**
**stdout:**
```
|test|
| s|
| |
|RandomWord|
|t|
|ff|
```
**Example2.txt**
```
test
s
RandomWord
t
ff
```
Dec 09 2023