If a file exists, >
will overwrite the file and >>
will append to the end of the file. If a file does not exist, both will create a new file.
Also, the echo
command automatically adds a newline after your string.
So
echo 1 > num.txt
echo 1 > num.txt
echo 2 >> num.txt
will create the following file:
1
2
Not this:
1 1 2
or
1 2
Furthermore, you cannot just modify a single line in a text file. You have to read the whole file, modify it in your code and then write to the whole file again.
Format:
[command] [> | >>] [filename]
>
saves the output of [command] into [filename].
>>
appends the output of [command] into [filename].
Examples:
echo Hello World > myfile.txt
saves "Hello World" into myfile.txt
echo your name is %name% >> myfile.txt
appends "your name is xxxx" into myfile.txt
dir C:\ > directory.txt
saves the directory of C:\ to directory.txt
Ways to create a file with the echo command:
ECHO. > example.bat (creates an empty file called "example.bat")
ECHO message > example.bat (creates example.bat containing "message")
ECHO message >> example.bat (adds "message" to a new line in example.bat)
(ECHO message) >> example.bat (same as above, just another way to write it)
If you want to create a file via the ECHO
command, in a specific directory on your computer, you might run into a problem.
ECHO Hello how are you? > C:\Program Files\example.bat
(This will NOT make a file in the folder "Program Files", and might show an error message)
But then how do we do it? Well it's actually extremely simple... When typing a path or file name that has a space included in it's name, then remember to use "quotes"
ECHO Hello how are you? > "C:\Program Files\example.bat"
(This will create "example.bat" in the folder "Program Files")
But what if you want to make a file that outputs a new file?
ECHO message > file1.bat > example.bat
(example.bat is NOT going to contain "message > file1.bat")
example.bat will just contain "message"... nothing else
Then how do we do this? Well for this we use the ^
symbol.
ECHO message ^> file1.bat > example.bat
(example.bat is going to contain "message > file1.bat")
Same goes for other stuff in batch
The next step requires you to have some knowledge about variables and statements:
click here to learn about variables | click here to learn about if and else statements
Variables:
SET example="text"
ECHO %example% > file.bat
(This will output "text" to file.bat)
if we don't want it to output "text" but just plain %example% then write:
ECHO ^%example^% > file.bat
(This will output "%example%" to file.bat)
IF/ELSE statements:
ELSE statements are written with "pipes" ||
IF ^%example^%=="Hello" ECHO True || ECHO False > file.bat
(example.bat is going to contain "if %example%=="Hello" echo True")
[it ignores everything after the ELSE statement]
to output the whole line then we do the same as before.
IF ^%example^%=="Hello" ECHO True ^|^| ECHO False > file.bat
This will output:
IF %example%=="Hello" ECHO True || ECHO False
If the variable is equal to "Hello" then it will say "True", ELSE it will say "False"
Using many ECHO
commands to create a batch file:
(
echo echo hi, this is the date today
echo date /T
echo echo created on %DATE%
echo pause >nul
)>hi.bat
The command interpreter treats the whole section in parenthesis as a single command, then saves all the output to hi.bat
.
hi.bat
now contains:
echo hi, this is the date today
date /T
echo created on [date created]
pause >nul