command > filename Redirect command output to a file command >> filename APPEND into a file command < filename Type a text file and pass the text to command commandA | commandB Pipe the output from commandA into commandB commandA & commandB Run commandA and then run commandB commandA && commandB Run commandA, if it succeeds then run commandB commandA || commandB Run commandA, if it fails then run commandB commandA && commandB || commandC If commandA succeeds run commandB, if it fails commandC
Success and failure are based on the Exit Code of the command.
In most cases the Exit Code is the same as the ErrorLevel
Numeric handles: STDIN = 0 Keyboard input STDOUT = 1 Text output STDERR = 2 Error text output UNDEFINED = 3-9 command 2> filename Redirect any error message into a file command 2>> filename Append any error message into a file (command)2> filename Redirect any CMD.exe error into a file command > file 2>&1 Redirect errors and output to one file command > fileA 2> fileB Redirect output and errors to separate files command 2>&1 >filename This will fail! Redirect to NUL (hide errors) command 2> nul Redirect error messages to NUL command >nul 2>&1 Redirect error and output to NUL command >filename 2> nul Redirect output to file but suppress error (command)>filename 2> nul Redirect output to file but suppress CMD.exe errors
Any long filenames must be surrounded in "double quotes".
A CMD error is an error raised by the command processor itself rather than the program/command.
Redirection with > or 2> will overwrite any existing file.
You can also redirect to a printer with > PRN or >LPT1
In a batch file the default behaviour is to read and expand variables one line at a time, if you use & to run multiple commands on a single line, then any variable changes will not be visible until execution moves to the next line. For example:
SET /P _cost="Enter the price: " & ECHO %_cost%
This behaviour can be changed using SETLOCAL EnableDelayedExpansion
Create empty files using the NUL device:
Type NUL >EmptyFile.txt
Copy NUL EmptyFile.txt
To prevent the > and < characters from causing redirection, escape with a caret: ^> or ^<
Redirect multiple lines by bracketing a set of commands:
( Echo sample text1 Echo sample text2 ) > c:\logfile.txt
If the filename or command is not found then redirection will set an Exit Code of 1
The CMD Shell can redirect ASCII/ANSI (the default) or Unicode (UCS-2 le) but not UTF-8.
This can be selected by launching CMD /A or CMD /U
With the default settings a UCS-2 file can be converted by redirecting it (note it's the redirection not the TYPE/MORE command that makes the encoding change)
TYPE unicode.txt > asciifile.txt
European characters like ABCàéÿ will usually convert correctly, but others like £¥ƒ€ will become random extended ASCII characters: œ¾Ÿ?
When a command is piped with '| batch_command ' this will instantiate a new CMD.exe instance, in effect running:
C:\Windows\system32\cmd.exe /C /S /D "batch_command"
This has several side effects:
Any newline (CR/LF) characters in the batch_command will be turned into & operators. (see StackOverflow)
If the batch_command includes any caret escape characters ^ they will need to be doubled up so that the escape survives into the new CMD shell.
Starting a new CMD shell also has a small (likely unnoticable) effect on performance.
For example, this syntax works, but would fail if the second or subsequent (piped) lines were indented with a space:
echo abc def |^
find "abc" |^
find "def"> outfile.txt
Multi-line single commands with lots of parameters, can be indented as in this example:
Echo abc def ^
ghi jkl ^
When redirecting the output of DIR to a file, you may notice that the output file (if in the same folder) will be listed with a size of 0 bytes. The command interpreter first creates the empty destination file, then runs the DIR command and finally saves the redirected text into the file.
The maximum number of consecutive pipes is 2042
DIR >MyFileListing.txt DIR /o:n >"Another list of Files.txt" DIR C:\ >List_of_C.txt 2>errorlog.txt DIR C:\ >List_of_C.txt & DIR D:\ >List_of_D.txt ECHO y| DEL *.txt ECHO Some text ^<html tag^> more text COPY nul empty.txt MEM /C >>MemLog.txt Date /T >>MemLog.txt SORT < MyTextFile.txt SET _output=%_missing% 2>nul FIND /i "Jones" < names.txt >logfile.txt (TYPE logfile.txt >> newfile.txt) 2>nul
“Stupidity, outrage, vanity, cruelty, iniquity, bad faith, falsehood,
we fail to see the whole array when it is facing in the same direction as we” ~ Jean Rostand (French Historian)
conIN$ and conOUT$ behave like stdin and stdout, or 0 and 1 streams but only with internal commands.
TYPE - Display the contents of one or more text files
Q245031 - Error when using the | pipe symbol
Successive redirections explained (1>&3 ) - Stack Overflow
Equivalent bash command (Linux): Redirection - Spooling output to a file, piping input.