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Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. cmd stderr Join them; it only takes a minute: Sign up How to capture stderr on Windows/DOS? up vote 34 down vote favorite 10 I want to capture the errors from a script into a file instead of to the screen. https://support.microsoft.com/en-us/kb/110930 In *nix, this is done with stderr redirection, usually echo "Error" 2> errorfile.log How do I do it in a CMD script under Windows? windows scripting batch-file cmd stderr share|improve this question edited Oct 9 '15 at 19:42 Peter Mortensen 10.2k1369107 asked Jan 27 '09 at 8:46 mik 4932914 add a comment| 2 Answers 2 active oldest votes up vote 43 down vote accepted For example: PSKILL NOTEPAD >output.txt 2>&1 This will direct stdout and stderr to a http://stackoverflow.com/questions/482678/how-to-capture-stderr-on-windows-dos file name output.txt. See Underused features of Windows batch files for more details. share|improve this answer answered Jan 27 '09 at 12:49 aphoria 12.4k34056 7 If you want them redirected to separate files, you can do mycommand >stdout.txt 2>stderr.txt –Kip Oct 24 '12 at 16:15 add a comment| up vote 19 down vote That should work in Win32, too. If you have already redirected stdout, and want stderr redirected to the same file, you must use the 2>& special form, rather than just specifying the same file twice. Otherwise you'll get a "file busy" error. share|improve this answer answered Jan 27 '09 at 8:50 unwind 254k38330460 This is also covered in Redirect stdout and stderr to a single file. –Peter Mortensen Oct 9 '15 at 20:50 add a comment| Your Answer draft saved draft discarded Sign up or log in Sign up using Google Sign up using Facebook Sign up using Email and Password Post as a guest Name Email Post as a guest Name Email discard By posting your answer, you agree to the privacy policy and terms of service. Not the answer you're looking for? Browse other questions tagged windows scripting batch-file cmd stderr or ask your own question. asked 7 years ago viewed 32888 times active 12 months ago Blog International salaries at Stack Overflow Visit Chat Linked 232 Hidden features of Windows batch files 357
4 – stdin, stdout, stderr Part 5 – If/Then Conditionals Part 6 – Loops Part 7 – Functions Part 8 – Parsing Input Part 9 – Logging Part 10 – Advanced Tricks DOS, like Unix/Linux, uses the three universal “files” for keyboard input, printing text http://steve-jansen.github.io/guides/windows-batch-scripting/part-4-stdin-stdout-stderr.html on the screen, and the printing errors on the screen. The “Standard In” file, known as stdin, contains the input to the program/script. The “Standard Out” file, known as stdout, is used to write output for display on the screen. Finally, http://ss64.com/nt/syntax-redirection.html the “Standard Err” file, known as stderr, contains any error messages for display on the screen. File Numbers Each of these three standard files, otherwise known as the standard streams, are referernced using the numbers 0, 1, and 2. Stdin is file standard error 0, stdout is file 1, and stderr is file 2. Redirection A very common task in batch files is sending the output of a program to a log file. The > operator sends, or redirects, stdout or stderr to another file. For example, you can write a listing of the current directory to a text file: DIR > temp.txt The > operator will overwrite the contents of temp.txt with stdout from the DIR command. The >> operator is a slight variant that appends the capture standard error output to a target file, rather than overwriting the target file. A common technique is to use > to create/overwrite a log file, then use >> subsequently to append to the log file. SomeCommand.exe > temp.txt OtherCommand.exe >> temp.txt By default, the > and >> operators redirect stdout. You can redirect stderr by using the file number 2 in front of the operator: DIR SomeFile.txt 2>> error.txt You can even combine the stdout and stderr streams using the file number and the & prefix: DIR SomeFile.txt 2>&1 This is useful if you want to write both stdout and stderr to a single log file. DIR SomeFile.txt > output.txt 2>&1 To use the contents of a file as the input to a program, instead of typing the input from the keyboard, use the < operator. SORT < SomeFile.txt Suppressing Program Output The pseudofile NUL is used to discard any output from a program. Here is an example of emulating the Unix command sleep by calling ping against the loopback address. We redirect stdout to the NUL device to avoid printing the output on the command prompt screen. PING 127.0.0.1 > NUL Redirecting Program Output As Input to Another Program Let’s say you want to chain together the output of one program as input to another. This is known as “piping” output to another program, and not suprisingly we use the pipe character | to get the job done. We’ll sort the output of the DIR commmand. DIR /B | SORT
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 Multiple commands on one line 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 Creating a new file Create empty files using the NUL device: Type NUL >EmptyFile.txt or 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 Exit Codes If the filename or command is not found then redirection will set an Exit Code of 1 Unicode 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) T