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Bash Redirect Error To File


Is the "1" a file descriptor or an argument to cmd? (answer: it's the FD). If you want to redirect both, stderr and stdout to the same file (like /dev/null, to hide it), this is the wrong way: # { echo OUTPUT; echo ERRORS >&2; } So if you have a file descriptor like: --- +-----------------------+ a descriptor ( n ) ---->| /some/file | --- +-----------------------+ Using a m>&n (where m is a number) you got a Join them; it only takes a minute: Sign up How can I redirect and append both stdout and stderr to a file with Bash? this contact form

Bash reads (stdin) from this terminal and prints via stdout and stderr to this terminal. --- +-----------------------+ standard input ( 0 ) ---->| /dev/pts/5 | --- +-----------------------+ --- +-----------------------+ standard output more hot questions question feed lang-sh about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology Life / Arts Culture / Recreation Let's continue with the right part of the second pipe: | cmd3 3>&- 4>&- --- +-------------+ ( 0 ) ---->| 2nd pipe | --- +-------------+ --- +-------------+ ( 1 ) ---->| The second is less efficient but behaves in ways that are useful in certain circumstances. (Read about "subshells" to learn more.) –dubiousjim Oct 19 '12 at 14:20 add a comment| up

Redirect All Output To File Bash

exec 1<>$LOG_FILE # Redirect STDERR to STDOUT exec 2>&1 echo "This line will appear in $LOG_FILE, not 'on screen'" Now, simple echo will write to $LOG_FILE. Reply Link iamfrankenstein June 12, 2014, 8:35 pmI really love: "command2>&1 | tee logfile.txt"because tee log's everything and prints to stdout . Using exec20.2. echo foo > file the > file after the command alters the file descriptors belonging to the command foo.

  1. Always place redirections together at the very end of a command after all arguments.
  2. Use the long form >foo 2>&1. (see: obsolete) # Good!
  3. In the same way, command 2> file will change the standard error and will make it point to file.
  4. I lied, I did not explain 1>&3-, go check the manual Thanks to Stéphane Chazelas from whom I stole both the intro and the example….
  5. asked 5 years ago viewed 98630 times active 1 year ago Get the weekly newsletter!
  6. because the shell descriptor of the while loop looks like: --- +-----------------------+ standard input ( 0 ) ---->| file | --- +-----------------------+ --- +-----------------------+ standard output ( 1 ) ---->| /dev/pts/5

Check your preferred UNIX®-FAQ for details, I'm too lazy to explain what a terminal is Both, stdout and stderr are output file descriptors. Dec 11 '15 at 15:36 add a comment| up vote 42 down vote In Bash 4 (as well as ZSH 4.3.11): cmd &>>outfile just out of box share|improve this answer edited it cause original logfile is allways owerwritten. Bash Redirect Stdout And Stderr To Different Files Linked 728 How can I redirect and append both stdout and stderr to a file with Bash? 364 Redirect stderr and stdout in a Bash script 56 Piping both stdout and

cat File # ==> 1234.67890 # Random access, by golly. | # Pipe. # General purpose process and command chaining tool. # Similar to ">", but more general in effect. Their difference is the convention that a program outputs payload on stdout and diagnostic- and error-messages on stderr. command < input-file > output-file # Or the equivalent: < input-file command > output-file # Although this is non-standard. It will open a new file descriptor pointing to file.

stdin, stdout, stderr When Bash starts, normally, 3 file descriptors are opened, 0, 1 and 2 also known as standard input (stdin), standard output (stdout) and standard error (stderr). Bash Redirect Stdout And Stderr To Same File Are there any 'smart' ejection seats? This will not cause STDERR to be redirected to the same file. There are other problems as well.

Bash Output To File

This is clearly a simple commmand with two arguments and 4 redirections cmd arg1 arg2 /dev/null >&2 # Good! { cmd1 <<<'my input'; cmd2; } >someFile # Bad. The man page does specify a preference for '&>' over '>&', which is otherwise equivalent. –chepner Jul 16 '12 at 20:45 6 I guess we should not use &> as Redirect All Output To File Bash Hehe... Bash Redirect Stderr To File Append exec 3>&1 1>logfile 2>&1 echo "Hello World" ls filedoesnotexist exec 1>&3 echo "my message" | tee -a logfile ls filedoesnotexistyet exec 1>>logfile echo "Hello again" ls filestilldoesnotexist exit results in the

cat *.txt | sort | uniq > result-file # Sorts the output of all the .txt files and deletes duplicate lines, # finally saves results to "result-file".weblink So the issue is, the line generating the error is an error in the script itself, not an error caused by an external command the script calls which has it's output script.sh 2>output.txt …stderr is not connected to terminal now, how can the scrip get know abot it?? STDERR to "where stdout goes" Note that the interpretion "redirect STDERR to STDOUT" is wrong. –TheBonsai May 18 '09 at 8:55 18 It says "append output (stdout, file descriptor 1) Bash Redirect Stderr To Stdout To File

Hot Network Questions Meaning of "soul-sapping" Verbs of buttons on websites How does Gandalf get informed of Bilbo's 111st birthday party? How do I redirect stderr to a file? Order Of Redirection, i.e., "> file 2>&1" vs. "2>&1 >file" While it doesn't matter where the redirections appears on the command line, their order does matter. http://sovidi.com/bash-redirect/bash-redirect-error-output-to-file.php Though it might work, I'm not sure if you can expect all applications to behave correctly with a closed stderr.

ls -l 2>&1 >&3 3>&- | grep bad 3>&- # Close fd 3 for 'grep' (but not 'ls'). # ^^^^ ^^^^ exec 3>&- # Now close it for the remainder of Bash Redirect Error To Variable in the first example you wrote: exec 1<>$LOG_FILE . Your version redirects err to out, and at the same time out to file. –Alex Yaroshevich Mar 8 '15 at 23:22 | show 1 more comment Your Answer draft saved

This might be useful to have optical nice code also when using here-documents.

Let us see how to duplicate them, starting with the classic 2>&1. I was looking for it around here and didn't find it. If not, why? Bash Redirect Error Output To /dev/null Finding a file starting with '-' dash Can Customs make me go back to return my electronic equipment or is it a scam?

It just confuses people, you are right. Let's see another use case. Wiki syntax is allowed: Please fill all the letters into the box to prove you're human. his comment is here The word WORD is taken for the input redirection: cat <<< "Hello world... $NAME is here..." Just beware to quote the WORD if it contains spaces.

Bash 4 introduced a warning message when end-of-file is seen before the tag is reached. The here-string will append a newline (\n) to the data. My modified script: filename="/home/ronnie/tmp/hello" date= $(date) echo "$date" >> $filename 2>> $filename #Also tried echo "$date" >> $filename 2>&1 I was thinking that above script will redirect the error test.sh: line no wonder I get all those emails from cron.

This is why pipes work. If you write a script that outputs error messages, please make sure you follow this convention! Finally, for the left part of the pipe: --- +-------------+ ( 0 ) ---->| /dev/pts/5 | --- +-------------+ --- +-------------+ ( 1 ) ---->| 1st pipe | --- +-------------+ --- +-------------+ The shell's error stream is not redirected at this point.

Also remember that Bash 4 &>> is just shorter syntax — it does not introduce any new functionality or anything like that. sorry for that : ( Here comes some additional tips. 0, 1, 2...9 are file descriptors in bash. 0 stands for stdin, 1 stands for stdout, 2 stands for stderror. 3~9 read -n 4 <&3 # Read only 4 characters. asked 7 years ago viewed 331430 times active 4 months ago Get the weekly newsletter!

To prevent an fd from being inherited, close it. # Redirecting only stderr to a pipe. All about redirection 3.1 Theory and quick reference There are 3 file descriptors, stdin, stdout and stderr (std=standard). As with >, < can be used to open a new file descriptor for reading, command 3

exec 3>&1 # Save current "value" of stdout. Often nothing. Is this safe to display MySQL query error in webpage if something went wrong? They will look like: --- +-----------------------+ standard input ( 0 ) ---->| /dev/pts/5 | --- +-----------------------+ --- +-----------------------+ standard output ( 1 ) ---->| file | --- +-----------------------+ --- +-----------------------+ standard

So what does this have to do with redirection?