Bash echo to stderr and stdout. log myprogram &> out.

Bash echo to stderr and stdout txt ) 2> >(tee stderr. Hence, you can achieve your ends in this specific I have a Bash script: #!/bin/bash echo this should be visible only in the stderr output but it is not 1>&2 exit 0 Also, I have a custom app that starts this script. /foo ) > log. log" echo "This goes to stderr. It redirects stdout but the timestamp added is of the time when the script finishes: Just add >&2 to the statement producing the output:. stdout one place and stderr another. That will be passed to the pipe with the tee application. log myprogram > out. >(tee log. txt' >&2 FWIW I'd write your code using a case statement instead of nested ifs (and tidy up a couple of things): #!/bin/env bash case $# in 0 ) dir='. Now let's take a look at your SSH case, the steps are similar to last time with just one Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company I currently have a bunch of installer scripts which log stderr/stdout to a log file that works well but I need to also redirect stdin for user responses to the same log file. sh 2>&1 | tee -a log Share. /script. How do I do that? This will work in any POSIX-compatible shell: ls good bad >/dev/null 2>&1 You have to redirect stdout first before duplicating it into stderr; if you duplicate it first, stderr will just point to what stdout originally pointed at. Redirecting `echo` Output to Stderr # Echo to stderr echoStderr() { # - if necessary, quote the string to be printed # - redirect stdout from echo to stderr echo "$@" 1>&2 # Or, use an alternate echo such one that colors textT # ${echo2} "$@" 1>&2 } # Print a DEBUG message # - prints to stderr and optionally appends to log file if ${logFile} is defined globally # - see I currently use this in my scripts: exec > >(tee -a "${FILE_Log}" ) exec 2> >(tee -a "${FILE_Log}" >&2) Basically you are telling bash to send the output (both stdout and stderr) to tee's stdin, and since tee is running in the subshell (within the parentheses), it will live as long as your script does. txt #stdout & stderr -> log & stdout And of course, if you want stdout you can just print regularly. In case you're unaware of such a thing, that's exactly what cat does if you don't give it any arguments. log How to print a line to STDERR and STDOUT in Bash? Posted on Mar 24, 2018 by Q A In QA. txt > this is bar echo "this is foo, again" >> foobar. exec > >(tee foo. Bash, zsh and some other shells also provide the shortcut. log 2>&1 # Older sh syntax # Log output, hide errors. readline()" inside a "while 1:" loop. log # New bash syntax myprogram > out. stdin. txt exists in my Ubuntu system. I know tee could copy stdout to file but that's not what I want. Asking for help, clarification, or responding to other answers. I've done some research and the furthest I could get was thanks to How to add timestamp to STDERR redirection. txt > this is bar > this is foo, again Gotcha. Have you an idea ? The $* bash variable don't give me this info. . Streams in Linux—like almost everything else—are treated as though they Using `echo` to Write to Stderr Basic Syntax of `echo` The `echo` command is one of the most commonly used commands in Bash, and it prints specified text to the terminal. txt | foo. Share . Let me take the matthew-wilcoxson example. You can use them to tell if your scripts are being piped or redirected. echo your message here Examples: $ echo Note that there's not really any such thing as "preserving line order" once you're at this point - they're two separate streams and separate processes, and it's quite possible that the scheduler runs one process for a while before it gives the other one a go, with the data kept in the kernel pipe buffer until it's read. For opening additional files, there remain descriptors 3 to 9. Both writes must be done in append mode (>> instead of >) otherwise both would This also has the downside that all output will be written to stderr if the process terminates unsuccessfully, and no intermediate status messages will be written during the execution of the program at allif it's worth the cost, one could write a program that reads from stdin, buffers a certain amount (say a line of text), checks that line of input against a regex that Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company #!/usr/bin/env bash set -e function generate_output() { echo This message goes to stderr 1>&2 echo This message goes to stdout } generate_output \ 1> >(tee <&0 >(cat > out. – Randall > Is exec 3>&2 correct? Yes. Follow answered Aug 15, 2014 at 17:33. { ( echo info; >&2 echo critical ) 2>&3 | logger -t mycoolscript; } 3>&1 1>&2 | logger -t mycoolscript -p 2 The first part ( echo info; >&2 echo critical ) simulate a program that output both on stdout and stderr. txt #stdout -> log echo "hi" | tee -a log. You can combine the two streams into one if you send it to a pipeline with |&, then all you need to do is find a pipeline component that writes its standard input to its standard output. However, it does not answer the OP's question on how to force STDOUT (which is where echo sends output) to go to STDERR in tcsh. File handle 2 is STDERR, redirected by 2>. Share. For example: echo hello &> all_output. There is only one socket and via one socket one stream of data can be sent, not two. log) 2>&1 set -x # I want to capture every line that's executed too cat 'foo' echo 'bar' sleep 2 I want to direct the output of a printf in a bash script to stderr instead of stdout. To redirect the output of the echo command specifically to stderr, we can use the “2>” operator in Bash. txt. #!/bin/sh echo "I'm stdout"; echo "I'm stderr" >&2; Is there a way to call that script such that only stderr would print out, when the last part of the command is 2>/dev/null, ie In case of bash it is possible to allocate a file descriptor dynamically: myscript. txt too:. sh. Follow answered Dec 1, 2012 at 9:43. i. Using ‘>&2’ Operator. I can think of a workaround to send both of echo output and wc -l to the terminal by sending one to stdout and stderr using: $ echo "test" | tee /dev/stderr | wc -l test 1 This way you will both sent to your terminal via stdout and stderr. txt) exec 2> >(tee -a logfile. So far, so good. It is sometimes useful to assign one of these additional file descriptors to stdin, stdout, or stderr as a temporary duplicate link. For testing, I created a command which outputs to stdout and stderr, and works the same in Zsh and bash: (echo stdout; echo 1>&2 stderr) prints. txt # Redirect all script output to a logfile as well as their normal locations exec > >(tee -a logfile. command 1>/path/to/stdout. The install scripts sometime call functions in a shared library (an include), which may also read user input. txt will add the text “World” to the end of the file. log 2>/path/to/stderr. Use echo With Process Substitution to Echo to stderr in Bash. If, for example, all the writes to stdout are not flushed, but all the writes to stderr are flushed, then they'll end up out of chronological order in the output file and on the screen. Redirect stderr to Great use case, but the wording of the question's title does not do it justice - perhaps something along the lines of 'persistent redirection of stdout and stderr in bash'. but when I try to redirect stderr into a different one, it seems to go through the stdout channel: $ ( echo stdout ; >&2 echo stderr ) > >( rev ) 2> >( cat ) tuodts rredts I can't use pipe because I want to keep the processing strictly separate: $ ( echo stdout ; >&2 echo stderr ) 2> >(rev) stdout rredts and this does weird things: This saves stdout on fd 3, copies stderr to stdout, copies fd 3 (the original stdout) to stderr, and then closes the temporary fd 3. " | tee -a 'err. This is appropriate, as POSIX defines stderr as the appropriate stream for "diagnostic output", which is a The tee command save a copy of the input it receives to a file while sending it to the stdout as well. sh didn't work in my Bash terminal. Note that there is internal buffering in xreadlines(), readlines() and file- object iterators ("for line in sys. The process substitution is a bashism, so it is not portable and will not work if bash is called as /bin/sh or with --posix. First thing I tried is create a fifo and using another shell to monitor stdout of the first shell. Curiously, ~/scripts/myscript. You will want to look into the trap built-in specifically for your case. Because I also echo other interactive messages $ { echo "stdout"; echo "stderr" 1>&2; } | grep -v std stderr $ stdout goes to stdout, stderr goes to stderr. Here’s an example: bash echo "This will be printed on stderr" 1>&2 Let's suppose that your log function looks like this (it just echos the first argument):. Both behave the same for me, in that they only show stderr. Afterwards, you're therefore free to change where stdout is pointing without affecting stderr. Here is another useful example where both stderr and stdout sent to the more command instead of a file: # find /usr/home -name . According to the example given, the first line written is Just an example. This tutorial will discuss how to echo to stderr in Bash. txt) creates process substitution that represents itself as a file (try echo >(:)) that could be accessed as bash myscript. The number 2 represents the file descriptor for stderr. So, you will not see the output of echo. In a local machine if you run a login shell (say one of Ctrl + Alt + F1~6), it starts a new shell for the user and the output (stdout and stderr) goes right on your monitor. txt For programmers with an understanding of the concepts of stdout and strerr, that's not a problem. profile 2>&1 | more. Tutorials; HowTos; Reference; en. I'll call your command banana. log, stderr to err. \033[31m switches to red and \033[0m switches back to uncolored. I have a bash file that I need to redirect all output to one file, debug log as well as to the terminal. Prompts are conventionally written to stderr on UNIX, so for prompting-related purposes, retaining the original stdout isn't generally called for. txt #stdout & stderr -> log echo "hi" |& tee -a log. The tee command then writes that to tempfile as well I want to split stdout so that it is printed both to stdout and stderr. There is no aliasing or reverting. txt > this is foo echo "this is bar" > foobar. I know I came here and did not get For testing, I created a command which outputs to stdout and stderr, and works the same in Zsh and bash: (echo stdout; echo 1>&2 stderr) prints. It does not in any way merge the two streams into one. You can use exec and process substitution to send stdout and stderr inside of the script to tee. exec 2>&1 | systemd-cat -t myscript. the_cmd 1> >(tee stdout. redirect stderr to stdout and stdout to /dev/null in order to get only stderr on your terminal. txt #stdout -> log & stdout echo "hi" &>> log. Explains how to redirect standard error in bash shell on Linux, macOS, BSD & Unix . You can also redirect both stdout & stderr to a file. Dunno what you were using ls for (example or otherwise), but it is dangerous to use for any kind of expansion due to how Bash defines a word. A quick and dirty solution would be to write my own printf implementation that did this and use it in lieu of either built in, but it occurred to me that I might not need to. Use echo and /dev/stderr commands to redirect echo output to stderr. 004s I can capture the output of the time command as described here and redirect it to a file: user$ ( time . I used append mode for both so that regardless of Please note that the pipe will catch stdout only, errors to stderr are not processed by the pipe with tee. Related questions. (The curly braces (along with the semicolons) in my example could be left out as well if they only contain one command and the whole thing is a one-liner. This might be the opposite of what you want if your default grep colour is red. So basically you use tee if you want to save your output to a file but still want to see on the screen. g. By default, stdout is displayed on the terminal. You can redirect both stdin and stdout with it. On systems other than Linux-based ones, you could use: logfile=/dev/stdout For Linux, that works for some types of stdout, but that fails when stdout is a socket or worse, if stdout is a regular file, that would truncate that file instead of writing at the current position stdout is in the file. log) 2> >(tee -a stderr. There's a really ugly way to capture stderr and stdout in two separate variables without temporary files (if you like plumbing), using process substitution, source, and declare appropriately. #!/bin/bash echo "Just an example. log cat test. I do this regularly within scripts and leverage the additional file descriptors to pass back additional I can time the execution of my program using BASH's builtin time command while combining stdout and stderr: user$ time . anubhava anubhava. log) 2> >(tee stderr. log echo "Fully logged command" Would write the following to stdout and to script. /foo 2>&1 stdout: stdout says hi stderr says hi stderr:: real 0m0. In your example you redirect the stderr of echo, but echo always sends its output to stdout, not The problem (especially when mixing stdout and stderr streams) is that there is reliance on the streams being flushed by the program. It sets the stdout FD of the echo process to be the same as it's FD for stderr. I'd like to do different things to the stdout and stderr of a particular command. However, I specifically want to echo some statements to stderr. It does use process substitution and requires Bash > v4 but also captures stdout, stderr and return code into First redirect stderr to stdout — the pipe; then redirect stdout to /dev/null (without changing where stderr is going):. DE; ES; JA; KO; Tutorial The 1>&2 redirects stdout to stderr. sh: # do some setup, e. Sometimes you may need the output streams to be analyzed for further processing, in a Reading the command from stdin will be the solution if you want to be able to do this with arbitrary bash commands, but a child bash process is not the same as a subshell; you'll need to make sure you export any variables and functions which you need to use in the commands (and unfortunately you cannot export bash arrays). Follow answered Jun 25, 2019 at 20:55. Here's some references: File descriptor 0 (FD0) is named STDIN; File descriptor 1 (FD1) is named STDOUT I suspect you would want to send the stdout/stderr to a file and edit it there, in which case you need: progname 2>&1 | tee tempfile ; textmate tempfile The 2>&1 redirects stderr (file handle 2) to go to the same place as stdout (file handle 1) so that both of them end up in a single stream. I tried. echo Hello world echo Hello world > file. As I said, this works when run interactively. log exec &> out. I'd like to know if there's a way in bash have the current command statement printed to both stdout and a log file, in addition to the command's output. :. command 2>&1 >/dev/null | grep 'something' For the details of I/O redirection in all its variety, see the chapter on Redirections in the Bash reference manual. – Charles Duffy { unsetopt multios; command 2>&1 1>&3 3>&- | stderr_command; } 3>&1 1>&2 | stdout_command To use, replace command with the command you want to run, and replace stderr_command and stdout_command with your desired pipelines. Here is a lengthy article on stdin, stdout and stderr: What Are stdin, stdout, and stderr on Linux? To summarize: Streams Are Handled Like Files. log 2> err. For a reason not known to me, the authors of make decided to echo the executed commands to stdout, which pollutes the latter. i would like to run grep on the output of the program, and redirect all matches to stderr while leaving the unmatched lines on stdout (alternatively, i'd be happy with getting all lines - not just the unmatched ones - on stdout ) You should map normal stdout to another file descriptor (4), make the file the default output, then use tee to redirect output to the new file descriptor through /dev/fd. Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company I want to know if there is a built-in BASH command that prints some text on stderr, just like the echo command that prints text on stdout. 0: /dev/tty, 1: /dev/tty, 2: /dev/tty The first thing that gets set up is the pipe. Here’s an example: bash echo "This will be printed on stderr" 1>&2 echo echo "== stdout now restored to default == " echo ls -al echo exit 0 appears to show what you want. Stack Overflow. I'd need to I'm looking for a solution (similar to the bash code below) to copy both stdout and stderr to a file in addition to the screen within ksh on Solaris. Something like: $ echo "FooBar" () FooBar FooBar $ where () is the redirection expression. I would like to redirect everything that goes to stdout (from my echo statements and all the tools output) to stderr. Related: How To Redirect Linux Output To File: A Comprehensive Guide. Usually, the echo command will print text to the console: echo "hello there!" The stdout of the echo program is taking its default path to be displayed on your I have a bash application that is producing some result, and I'd like to echo the result to either stdout or to a user chosen file. – For a command that prints to both stdout and stderr like this one: mycommand { echo "stdout"; echo "stderr" >&2; } If I issue that normally, I see all the output: $ mycommand stdout stderr I can redirect stdout or stderr to /dev/null so it doesn't get printed: Some of the targets in my Makefile run programs whose output (which they send to stdout) I am interested in. The command stderr is mainly used to keep a record of errors during the execution of any command. ' Bash print stderr only, not stdout [duplicate] Ask Question Asked 10 years, 4 months ago. Append Both Stdout and Stderr to a File in Bash. You can still grep the text. stdout stands for “standard output” and it’s the default output stream in Bash. Any thoughts on this? – Lino. We show you I've written a bash script. other-script's stdin gets connected to the pipe, and script's stdout gets connected to the pipe, so script's file descriptors so far look like: Redirect stderr and stdout in Bash [duplicate] (15 answers) Closed 8 years ago. To (. The only reasonable implementation I can imagine is shell-builtin. And for those who "seeing is believing", a quick test: (echo "Test Out";>&2 echo "Test Err") > >(tee stdout. The correct, portable way to redirect both stderr and stdout to /dev/null is: >/dev/null 2>&1 To get the stderr of cmd while leaving its stdout untouched (here by using fd 3 to bring the original stdout (copied with 3>&1) inside the command substitution (restored with >&3 after we've redirected fd 2 to the pipe created by the command substitution with 2>&1)). So, in your JAVARESULT variable you'll just have to append: 2>&1 What you're saying here is: redirect stderr (file descriptor 2) to stdout (file descriptor 1). Of course you'd need process substitution to pass stderr output to tee: { Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company The following solution works only if bash supports /dev/fd/NUM. cmd |1 stdout_1 | stdout_2 |2 stderr_1 | stderr_2 where stdout_x is a command specifically for stdout and stderr_x is specifically for stderr. txt redirects both stdout and stderr to the file all_output. txt cat foobar. Stack Exchange Network. 1)? Both stderr and stdout of your program become block buffered I would expect, actually, that with "tee" sending the output to the file, and stderr redirected to the file, that you would see this line twice in the file. To view both stdout and stderr on the console and send both streams to a log, redirect stderr to stdout as shown below: progam. stdin, stdout, and stderr are streams attached to file descriptors 0, 1, and 2 respectively of a process. log: + echo 'Fully logged command' Fully logged command Firstly: echo "foo" >&2 This does not redirect any/all of echo's output to stderr; it is a s/h equivalent to echo "foo" 1>&2. Then use it like this: silence /path/to/the_script Notes: Not suppressing errors is achieved by leaving stderr Another possibility, with some bash flavours, is to turn on the pipefail option:. By using this operator, we can Using /dev/stderr. e. without loosing information what data is Where I pipe the output from echo ${FILE} into grep, it still outputs to stdout, something I want to avoid. You can use 3>&1 and /dev/fd/3 when calling the function to achieve your result: Thanks for contributing an answer to Stack Overflow! Please be sure to answer the question. Improve this answer. /command >/dev/null 2>&1, which No, not necessarily. txt >&2) date ls . If you just want stderr, then do. stdin") which is not influenced by this option. txt >&2 ) This redirects both stdout and stderr separately, and it sends separate copies of stdout and stderr to the caller (which might be your terminal). 1 Make a You could also log both stdout & stderr to different level in syslog. log special_echo "starting" # many other commands go here # which output both the stdout and stderr # also some special_echo See from the image, that my test file log. echo "Too many operands. Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. How can I command > >(tee -a stdout. (Well, it doesn't have to be built-in, but providing it as an external program would be immensely difficult. Provide details and share your research! But avoid . For example, the command ls / /foo will produce both stdout output and stderr output, so we can use it as a test case. grep only sees stdout , hence stderr prints to the terminal. Redirecting stdout. 0. ) I just now remembered that newer bash also provides a help shell-builtin that you might like: help exec. It invokes a few 3rd party tools. txt stdout if [[ $(<cmd>) ]]; then; echo error; else echo ok; fi cound be written as <cmd> || { echo error; } && { echo ok; }, which is a bit less verbose and gives the command a bit more prominence. First we pipe stdout to /dev/null, then we convert stderr to stdout, because Unix pipes will only operate on stdout. For example, the command ls | wc -l will send the output of “ls” to “wc To overwrite one file's content to another file you use the single greater than sign, using two will append. I use a buil I was wondering if it was possible to tell bash that all calls to echo or printf should be followed up by a subsequent call to fflush() on stdout/stderr respectively?. I've tried this: $ echo $(tty) # or (a lot better) simply: tty /dev/pts/4 $ echo aa | echo $(tty) not a tty Which means that the right side of a pipe is not connected to a tty. Then use it like this: silence /path/to/the_script Notes: Not suppressing errors is achieved by leaving stderr If it outputs to stderr as well you'll want to silence that. The basic syntax is as follows: echo [OPTIONS] [STRING] For example: echo "Hello, World!" This command outputs Hello, World! to `stdout`. In a Bash script, I need to redirect the output of a command to a variable, while also streaming unbuffered output to the terminal. Let’s start by understanding what stdout is. The idea of using named pipes posted by @DukeLion is a nice one also. log Confirm if stderr outputs to terminal and file rm -f test. You can't send stdout and stderr (two streams) via one handle (I mean, without like inter-mixing them, i. Note that 'exec &>' redirects both stdout and stderr, we could redirect them separately if we like, or change to 'exec >' if we just want stdout. $ (echo "this is stdout"; echo "this is stderr" >&2) | grep . The stdout is empty and the stderr contains the text provided. Try this script: echo "Visible 1" >> /dev/stderr exec 3>&2 exec &> /dev/null echo "Invisible" >> /dev/stderr exec 2>&3 echo "Visible 2" >> /dev/stderr Again, this works interactively but fails via cron. The redirection operator >&2 resembles the same This article will show different methods to redirect the echo output to stderr in Bash. Prompting on stderr is what read -p does; what bash itself does (like other shells); etc. r. I've been using a function outputting odd numbers to stdout Guarantees that ordering between stdout and stderr is precisely in line with the write calls only exist when they're both served by the same file descriptor, and you can't have them served by the same file descriptor while directing their output to different places, even if they're recombined later. – This is a good way to get STDOUT and STDERR split from a command sending output to both, and send them to files. You can test if the file descriptor is open or not by attempting to redirect to it early and if it fails, open the desired numbered file descriptor to something like /dev/null. 4. I thought about adding a custom read function but this will require altering the shared library and The following Bash syntax will hide output to stdout, but will still show stderr. It may redirect the output of echo to stdout and stderr. In fact, echo command does not even return any error or nonzero return code. I have the following shell script that echos output to the log and errors to err_file. In the case of the first command, I suspect that this is because I am combining stdout and stderr (2>&1) before I pipe it to the second tee, but if this were the case I would expect to see both stdout and stderr in the tee2. command 2>/path/to/log. #!/bin/bash exec 1>>result. ) Is there a way to redirect both stdin and stdout to netcat. log" >&2 echo "This goes directly to real stderr" >&4 Note that redirections are processed in the order they're given on the command line left-to-right. From that page: But some people won't accept either the loss of separation between stdout and stderr, or the desynchronization of lines. echo "Some console and log file message" | tee /dev/fd/3 to write a message to both the console and the log file - tee sends its output to both its own fd 1 (which SSH is a protocol that lets you login into the remote machine just like you would login on a local machine. I experimented a little and found that appending 1>&2 to the printf, as shown in the example below At first, when your terminal and shell starts, both STDOUT and STDERR points to the terminal output. You can supply the Explains how to redirect output (stdout) and errors (stderr) to /dev/null under UNIX / Linux / BSD shell scripting or cron jobs. There is socat, which is a more advanced netcat. However, for interns, the only effect in both cases is: the output is gone and was redirected into a file. sh | tee stderr Of course, how should stderr actual To add on to the answer from rsp and respond the question in the comments of that answer from @MattClimbs. txt 2>&1. 003s sys 0m0. Here's the concrete task I'm trying to accomplish. See from the image, that my test file log. Note that the sequence of I/O redirections is interpreted left-to-right, but pipes are set up before the I/O $ echo 1 | tee /dev/stdout | sed 's/1/2/' 2 2 output 2 twice instead of 1 and 2 . Barmar Barmar. log is a dummy command that will be replaced by something else when I figure out how to make this work. This way the data will be appended to the specified file instead of I'd like to have the stdout of a command replicated to stderr as well under bash. Note that doing this one loses the guarantee that ordering will be consistent between the two streams -- if you write, say, five lines to stdout, one line to stderr, and five more lines to stdout, it's not at all guaranteed that the line written to stderr will have five stdout lines before it and five after it when it finally gets flushed. stdout stderr Now I do your redirection: (echo stdout; echo 1>&2 stderr) 2>&1 >/dev/null Here, I see on bash and zsh. I just want to be able to send the output from a printf to stderr instead of to the default of stdout. 784k 67 67 gold badges 593 593 silver badges 661 661 bronze badges. Add a 2>&1 doesn't point stderr to stdout. create script. txt file, which I don't - I only see stderr! In the case of the second command, my impression from reading the answer I This makes output from script go from the process, through the pipe into the sub background process of 'tee' that logs everything to disc and to original stdout of the script. Instead, 2>&1 points stderr to where stdout is currently pointed, and not to stdout itself. The trick with 2>&3 come from that answer, to be able to # Save old stdout exec 3>&1 # Redirect stderr to pipe, stdout to saved descriptor, pipe goes to tee app_command 2>&1 >&3 | tee errorfile # close temporary descriptor now that app is done exec 3>&- Share. ls good bad &>/dev/null which is convenient on the command-line but should be avoided in scripts echo "hi" >> log. 0. " Surprisingly, there is no output (to either stdout or stderr) before I have sourced the actual_script. pipefail. 3. I tried $ echo 'ee' | tee /dev/stdout | foo but it does not work since tee output to /dev/stdout is piped to foo However, there is another method. stderr [2] The file descriptors for stdin, stdout, and stderr are 0, 1, and 2, respectively. So doing an echo "test" immediately after the exec will not be visible in the output. > Do your cron jobs run under the same user and group id as your As a convenience, the redirection &> can be used to direct both stdout and stderr to the same destination. We can also redirect output to another command using a pipeline. socat TCP4-LISTEN:5556,reuseaddr,fork EXEC:"cat - /etc/redhat-release" Bash redirection: save stderr/stdout to different files and still print them out on a console. log myprogram &> out. log >/tmp/stdout. The idea is that a buffer is more efficient for stdout, but errors should not be delayed by a buffer. Update 2: From Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company Usually, output goes either to file descriptor 1 (stdout) or 2 (stderr). You can mimic such a command with a function: banana() { echo "banana to stdout" echo >&2 "banana to stderr" } Use the >&2 operator to redirect the echo output to stderr in bash. My expectation however. I need to redirect both stdout and stderr to the debug and log it for all commands in the script. log() { echo "$1"; } To save the stdout of mysqldump to some file and call your log() function for every line in stderr, do this: stdin, stdout, and stderr are three data streams created when you launch a Linux command. 9 Bash redirection: save stderr/stdout to different files and still print them out on a console. Note that if you're using these to make log files, then unless you're sending the outut to _uniquely_named_ (eg date-and-time-stamped) log files, then if you run would send stdout and stderr output into the log file, but would also leave you with fd 3 connected to the console, so you can do . I am wondering if there is a simpler Correct, file handle 1 for the process is STDOUT, redirected by the 1> or by > (1 can be omitted, by convention, the command interpreter [cmd. log echo "This is stdout" | tee -a /dev/fd/2 echo "This is stderr" >&2 echo "This is stdout 2" | tee -a /dev/fd/2 echo "This is stderr 2" >&2 echo "This is stdout 3" | tee -a /dev/fd/2 echo "This is stderr 3" >&2 echo "This is stdout 4" | tee -a Please see BashFAQ/106. When you run a command, any output it generates is usually directed to stdout. and it worked, stdout and stderr were directed to systemd's journal. Pls help #!/bin/ksh echo "paramPassed: $0 $#" I don't really know what you mean by reading the value of stderr or stdin, but I can tell you why that cat /dev/stderr would keep running: it's waiting for data to read from the fd. Most probably because stderr is piped to logStd(). log >&2) Personally, when I try, I have this result: user@computer:~$ (echo "Test I have a bash script and want to write STDOUT to a log file only (not to the console) STDERR to the same log file and to the console I tried #!/bin/bash main() { echo "HELLO" Skip to main content. Your command echo "potato" >&2 is asking to redirect STDOUT to what STDERR points to. sh > generated_named_pipe 2>&1. 779k 56 56 gold badges 540 540 silver badges 652 652 bronze badges. log echo "This goes to stdout. Visit Stack Exchange For example, echo World >> output. It has a few echo statements. E. 1. log 2>>full. If set, the return value of a pipeline is the value of the last (rightmost) command to exit with a non-zero status, or zero if all commands in the pipeline exit successfully. it should put \033[31m before and \033[0m after everything that comes from stderr. You can append both stdout and stderr instead of just redirecting at the same time to the same file. log >&2) Beware than if you use bash you could have some issue. For example, consider the following script #!/bin/bash # all stdout and stderr go to out. exe] knows to handle that). It keeps the output in order. txt let x=1/0 let x=1/0 2> file2. I am not asking about redirecting either stderr or stdout from where ever they are currently routed. The following code works great in the bash shell: #!/usr/bin/bash # Clear the logfile >logfile. this is stderr this is stdout This will result in stdout being highlighted with the default grep colour and stderr being white. On Linux, we can view this with: Bash supports colors, i. Process This leads us to a Bash script that can silence other Bash scripts, except echos in them: #!/bin/bash echo() ( >&3 command echo "$@" ) export -f echo exec 3>&1 >/dev/null "$@" Save it as silence somewhere in PATH, make it executable. stdout is buffered, stderr is not. log ping e. sh: Printing to stderr (Note that the above command is different then . Put that somewhere near the top, then any and all command output, echo, I have a large bash script and I want to globally redirect all stdout/stderr to a file, except some progress indicators such specific echo messages. myprogram > out. So then for: { echo "foo" 2>&1 >&2 ; } > /dev/null Here, the stderr FD for the echo process is set to the stdout FD; then the stdout FD is function out { echo stdout echo stderr >&2 } x=${ { y=$(out); } 2>&1; } typeset -p x y # Show the values produces. Thus this command has no effect at all. I have a program (server) and I am looking for a way (script) that will redirect (or better duplicate) all its stdout to file and add timestamp for each entry. If you want to log errors (from stderr), use: command 2>&1 | tee /path/to/logfile This means: run command and redirect the stderr stream (2) to stdout (1). log # Send both stdout and stderr to out. $ echo 'ee' | tee output. What we are doing here is redirecting the stdout into the stderr channel . Syntax: In the syntax above, you can Bash echo to STDERR - echo to the standard error or stderr We all know that the bash echo command prints everything that you give after that. It came from the ABS , where there is a small amount of discussion and other relevant information. zsh behaves the way I like $ zsh $ which clang > /dev/null 2&>1 && echo clang || echo gcc clang $ which doesntexist > /dev/null 2&>1 && echo doesntexist || echo gcc gcc echo gcc gcc But, in bash: $ bash $ which The 2>&1 command really redirects stderr to stdout, but it seems in most cases this construction won’t work as it was thought out. or -c 6 2>&1 | tee test. A hard way around this problem that involves swapping file descriptors was suggested here. Also, given the solutions found, I suggest updating the question to make it focus on the intent rather than your original solution attempt. So, why would we want to redirect stdout? Well, there are several With a simple example (echo use here is just for illustration purpose) : $ echo 'ee' | foo ee <- the output I would like to see. log)) cat > out. " @GGG: correct; any POSIX-compliant shell will provide an exec shell built-in. You echo -n >outputfile; bash -c "echo stdout >&1; echo stderr >&2" 2>&1 >>outputfile | tee --append outputfile; echo "outputfile:"; cat outputfile Edit 1: This works by writing stdout (only) to the file, making sterr stdout so that it goes through the pipe, and having tee write its output to the same file. I'm not sure that this is even possible, because when two parallel processes (or even a single process) writes to both 1 for stdout; 2 for stderr; What you want to do is redirect stderr to stdout, and then redirect stdout to a file. If you close a file descriptor, you'll have to do so for every numbered descriptor, as &> (below) is a special BASH syntax incompatible with >&-: /your/first/command >&- 2>&- Be careful to note the order: >&-closes stdout, which is what you want to do; &>-redirects stdout and stderr to a file named exec 3>&1 4>&2 2>/tmp/stderr. How to have stdout and stderr to both console and file, having red stderr lines and "stdout and stderr being displayed as they are being produced" (See Fig. sh but it doesn't work. 1 -c 6 2>&1 | tee test. sh {FD} Let's assume stdin (fd 0), stdout (fd 1) and stderr (fd 2) are all connected to a tty initially, so . $ . 017s user 0m0. On the systems I can test this on, both output fd's are connected to the terminal just like stdin is, and reading from them works just fine. If you want to redirect all echo statements to stderr, you can accomplish this by redirecting stdout to stderr using the “2>&1” operator. tee outputs twice to stdout , and tee process's stdout is redirected to sed by the pipe, so all these outputs run through sed and you see double 2 here. -u Force stdin, stdout and stderr to be totally unbuffered. On systems where it matters, also put stdin, stdout and stderr in binary mode. The stderr will then get converted to stdout which is piped to tee which appends it to the log (if you are have Bash 4, you can replace 2>&1 | with |&) and sends it to stdout which will either appear on the tty or can be piped to another command. echo "Some console message" 1>&3 to write a message just to the console, or. In zsh, it will not proceed to the next statement until the tees have finished. Outputs stdout and stderr to terminal and catch stdout and stderr into file Test if stdout and stderr outputs to terminal and file rm -f test. I don't want to use temporary io-redirection. log Thanks! =D In bash script, echo "error" 1>&2 | tee -a log will print stderr in screen but no log to file, how to do these at same time? Skip to main content. If so you can explicitly set the grep colour to green: $ GREP_COLORS='ms=01 #!/bin/bash # testing STDOUT & STDERR echo "This is an error" >&2 echo "This is normal output" All we had to add is >&2. Here are some basic examples using redirection and piping. How to redirect STDERR to STDOUT in Linux. But when I start the script from the console (physical i have a program that outputs to stdout (actually it outputs to stderr, but i can easily redirect that to stdout with 2>&1 or the like. stderr but of course written to standard output, because 2>&1 first redirects the stderr of the I would like to test in my bash script where stdout and stderr are directed, or more precisely, if they have been redirected. You can do that by redirecting file descriptor 2: # Send stdout to out. 173 How do I get both STDOUT and STDERR to go to the terminal and a log file? 16 Write STDOUT & STDERR to a logfile, also write STDERR to screen. This is equivalent to echo hello > all_output. sh &> | systemd-cat -t myscript. " >&2 and if you want it to be appended to a file named err. In any case, you have redirected stderr (and stdout), so the line does go to stderr, but that has been redirected to the file. This sounds like a job for tee but the syntax is evading me - . Sometimes you may need the output streams to be analyzed for further processing, in a Redirecting stderr to stdout to a file or another command. I still need to find a way to do this inside my script for when other programs call my script. log ping 127. log If you want to redirect all echo statements to stderr, you can accomplish this by redirecting stdout to stderr using the “2>&1” operator. Commented Jun 4, 2021 at 14:11. At the prompt of an interactive shell in a terminal or terminal emulator, all those 3 file descriptors would refer to the same open file description which would have been obtained by opening a terminal or pseudo-terminal device file (something like /dev/pts/0) in First, you should avoid echo to output arbitrary data. For example: runme. It did not work, I don't know why: tty1 $ mkfifo stdout $ exec 1>stdout $ echo "Hello stdout" tty2 $ tail -f stdout $ # nothing here How can I reconnect my closed STDOUT and STDERR after all? Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company stderr and stdout should be sent to the log() function which will make sure to log the output to an log file according to specific log format (simplified in the example below) Issue with current code below: Step 1 is not trapped by onexit function and script is continuing to Step 2. Redirect Stderr to Stdout to Pipe to Another Command. I have a probably pretty easy beginner question: How do I echo from a shell script into both stdout and stderr? I know that I can echo to stderr echo "foo" 1>&2 but I need the output in both. I think it's a simple fix, but it's escaping me. I tried some Googling but nothing worked. I would like to make a small bash-wrapper that reliably puts out stderr in red, i. It's not easy to have your cake and eat it, too. Something like. echo "this is foo" > foobar. You can do this with any combination of streams you wish, just using those two basic commands. About; Products OverflowAI; Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; To get the stderr of cmd while leaving its stdout untouched (here by using fd 3 to bring the original stdout (copied with 3>&1) inside the command substitution (restored with >&3 after we've redirected fd 2 to the pipe created by the command substitution with 2>&1)). log)) \ 2> >(tee <&0 >(cat > err. In Bash, how to print a string as a line to STDOUT? That is, the string and the newline character, nicely? And similarly, how to print the line to STDERR? In Bash, you can simply use the echo command: echo "your message here" or. This leads us to a Bash script that can silence other Bash scripts, except echos in them: #!/bin/bash echo() ( >&3 command echo "$@" ) export -f echo exec 3>&1 >/dev/null "$@" Save it as silence somewhere in PATH, make it executable. The app captures both - stdout and stderr. /doit >> log) 2>&1 | tee -a log This will take stdout and append it to log file. /stdout-stderr. sh 2>&1 >/dev/null | grep err . In theory at least, stdout (file descriptor 1) and stderr (file descriptor 2) are different. Redirections are executed from left to right, so your version copies the old stdout to stderr, then redirects stdout to /dev/null. To work around this, you will want to use "sys. rml dromsw xum snsli rdf coeujy zqxojea dqniv ycqqap bfoef