Print To Standard Error
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Print To Stderr C++
Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users fprintf stderr c Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 6.2 million programmers, just like you, helping each other. Join them; it only takes a c stderr minute: Sign up Error checking fprintf when printing to stderr up vote 8 down vote favorite 3 According to the docs, fprintf can fail and will return a negative number on failure. There are clearly many situations where it would be useful to check this value. However, I usually use fprintf to print error messages to stderr. My code will usually look
Fprintf Stderr Example
something like this: rc = foo(); if(rc) { fprintf(stderr, "An error occured\n"); //Sometimes stuff will need to be cleaned up here return 1; } In these cases, is it still possible for fprintf to fail? If so, is there anything that can be done to display the error message somehow or is there is a more reliable alternative to fprintf? If not, is there any need to check fprintf when it is used in this way? c share|improve this question asked Jan 31 '11 at 0:18 Rupert Madden-Abbott 6,003104055 add a comment| 5 Answers 5 active oldest votes up vote 11 down vote accepted The C standard says that the file streams stdin, stdout, and stderr shall be connected somewhere, but they don't specify where, of course. It is perfectly feasible to run a program with them redirected: some_program_of_yours >/dev/null 2>&1 &- 2>&-
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C Fprintf
each other. Join them; it only takes a minute: Sign up echo that outputs to stderr up vote 479 down vote favorite 83 Is there a standard Bash tool that acts like echo but outputs to stderr rather than http://stackoverflow.com/questions/4846562/error-checking-fprintf-when-printing-to-stderr stdout? I know I can do echo foo 1>&2 but it's kinda ugly and, I suspect, error prone (e.g. more likely to get edited wrong when things change). bash share|improve this question edited Aug 19 '14 at 22:36 Steven Penny 1 asked Jun 7 '10 at 14:36 BCS 25.6k43146247 add a comment| 13 Answers 13 active oldest votes up vote 477 down vote accepted This question is old, but you could do this, which facilitates reading: >&2 http://stackoverflow.com/questions/2990414/echo-that-outputs-to-stderr echo "error" The operator '>&2' literally means redirect the address of file descriptor 1 (stdout) to the address of file descriptor 2 (stderr) for that command. depending on how deeply you want to understand it, read this: http://wiki.bash-hackers.org/howto/redirection_tutorial To avoid interaction with other redirections use subshell (>&2 echo "error") share|improve this answer edited Apr 8 at 7:25 Mateusz Konieczny 418519 answered May 8 '14 at 18:59 Marco Aurelio 5,0341913 81 alias errcho='>&2 echo' –BCS Aug 5 '14 at 21:29 3 @macmac, could you offer an explanation of this syntax or a link to more information? –allonhadaya Sep 25 '14 at 23:13 8 @allonhadaya, the operator '>&2' literally means redirect the address of file descriptor 1 (stdout) to the address of file descriptor 2 (stderr) for that command. depending on how deeply you want to understand it, read this: wiki.bash-hackers.org/howto/redirection_tutorial –John Morales Jan 6 '15 at 14:21 13 @BCS I dunno about using an alias in a shell script. It would probably be safer to use errcho(){ >&2 echo $@; } –Braden Best Jul 13 '15 at 21:52 34 In the nearly 40 years that I've been using Unix-like systems it has never occurred to me that you could put the redirect anywhere but at the end. Putting it up front like this makes it much more obvious (or "facilitates reading" as @MarcoAurelio says).
concept of standard input, standard output, and standard error. This section is for the rest of you. Standard output and standard error (commonly http://www.diveintopython.net/scripts_and_streams/stdin_stdout_stderr.html abbreviated stdout and stderr) are pipes that are built into every UNIX system. When you print something, it goes to the stdout pipe; when your program crashes and prints http://www.java2s.com/Code/Java/Development-Class/Outputtostandardoutputandstandarderrorandinputfromstandardinput.htm out debugging information (like a traceback in Python), it goes to the stderr pipe. Both of these pipes are ordinarily just connected to the terminal window where you are print to working, so when a program prints, you see the output, and when a program crashes, you see the debugging information. (If you're working on a system with a window-based Python IDE, stdout and stderr default to your "Interactive Window".) Example10.8.Introducing stdout and stderr >>> for i in range(3): ... print 'Dive in' Dive in Dive in Dive in >>> print to stderr import sys >>> for i in range(3): ... sys.stdout.write('Dive in') Dive inDive inDive in >>> for i in range(3): ... sys.stderr.write('Dive in') Dive inDive inDive in As you saw in Example6.9, "Simple Counters", you can use Python's built-in range function to build simple counter loops that repeat something a set number of times. stdout is a file-like object; calling its write function will print out whatever string you give it. In fact, this is what the print function really does; it adds a carriage return to the end of the string you're printing, and calls sys.stdout.write. In the simplest case, stdout and stderr send their output to the same place: the Python IDE (if you're in one), or the terminal (if you're running Python from the command line). Like stdout, stderr does not add carriage returns for you; if you want them, add them yourself. stdout and stderr are both file-like objects, like the ones you discussed in Section10.1, "Abstracting input sources", but they are both write-only. They have no read method, o
LDAPJPAJSPJSTLLanguage BasicsNetwork ProtocolPDF RTFReflectionRegular ExpressionsScriptingSecurityServletsSpringSwing ComponentsSwing JFCSWT JFace EclipseThreadsTiny ApplicationVelocityWeb Services SOAXMLOutput to standard output and standard error; and input from standard input. : Console«Development Class«JavaJavaDevelopment ClassConsoleOutput to standard output and standard error; and input from standard input. import java.io.BufferedReader; import java.io.InputStreamReader; public class InputOutputDemoStandardInputOutput { public static void main(String[] a) throws Exception { //Write characters to standard output and standard error: System.out.println("std output"); System.err.println("std error"); //Read characters from standard input (the keyboard): System.out.print("Type some characters and press Enter: "); BufferedReader bisr = new BufferedReader(new InputStreamReader( System.in)); String response = bisr.readLine(); System.out.println("You typed: '" + response + "'"); //Read a byte from standard input (the keyboard): System.out.print("Type one character and press Enter: "); byte b = (byte) System.in.read(); System.out.println("First byte of your input is: " + b); } } Related examples in the same category1.Turn System.out into a PrintWriter2.VarArgsDemo - show 1.5 variable arguments3.How to read from standard input4.How to deal with the console parameters5.Read input from console6.Command line input7.Read an int from Standard Input8.Read an int from Standard Input, using 1.59.SimpleCalc -- simple calculator using 1.5 java.util.Scanner10.Show use of Argv to get an integer value from command line11.Java program to calculate the area of a circle12.Java program to demonstrate menu selection13.Utility class for printing aligned columns of text14.Processing the command line15.A representation of the command line arguments passed to a Java class' main(String[]) method16.Helper class for storing long command lines inside temporary file.17.CommandLine Parser18.This parses command line arguments optimized for ease of programmer use.19.Console read and write Utilsjava2s.com |Email:info at java2s.com|© Demo Source and Support. All rights reserved.