Bash repeat command until success. Users can specify any executable file in the command lists.

Bash repeat command until success If I was sufficiently motivated, and felt considerate of my future successors trying to understand what I did, I'd probably wrap the confusion in a shell script and just call it with repeat. A slight variation to the previous answer, we can make the bash script sleep for a while, if we need to wait before testing the completion of the Python code. Otherwise, we may need to keep checking the Terminal window to verify whethe To retry a command in Bash, you can use a while loop. " will echo the given string 100 times and then stop. Exit status of a command. Repeating a command is one of the most commonly used operations when working with Linux scripting. Read More at @cgseller If you want to use multiple commands (like pipelines | or lists ;, &, &&, ||) between if and then you simply put them there like this: if ssh invalid | logger ; then echo "hi"; fi--- If you really want to enclose the command list once more you can use the curly {} or round brackets. CMD may be a simple command with separately specified arguments, if any, or a single string containing one or more ;-separated commands (including arguments) - in the former case the command is directly executed by bash, in the latter the string is passed to \`bash -c\`. sh script: #!/bin/bash psql -U postgres -1 -f file1. Note that while quotes are a way to protect white space and other special characters on the shell command line, the quotes don't exist any more within the Bash about repeat until. bash-aliases Second, paste these lines at the bottom of the file and save: repeat() { n=$1 shift while [ $(( n -= 1 )) -ge 0 ] do "$@" done } Third, either close and open again your terminal, or type:. 0. This tutorial explains the basics of the until loop in Bash. The until loop is a crucial feature of Bash scripts that executes a code block repeatedly until a specific condition becomes true. sh and added a line #!/bin/bash at the top. Is You can check the result of a command in the environment variable $? This variable will hold the value 0 if the last command executed was successful. Try to remotely login to it via ssh. ". A shell command to run 'x' number of times while a command Well, I guess you have sort of a point, but it still really feels like using a finely crafted engine block as a hammer. while Repeat a command until the command succeeds. How can i do that? batch-file; Share. – shellter. /test. Thanks! – The until command is identical to the while command, ex‐ cept that the test is negated: list-2 is executed as long as the last command in list-1 returns a non-zero exit status. Here you want: until sudo umount mount do sleep 0. In bash, you are given three types of loops: for, while, and until loop. For example, % repeat 100 echo "I will not automate this punishment. Thanks! – @GabrielStaples 1. Bash - Repeat a input n amount of times (user inputted) 2. Batch file - check if command is OSTechNix published a brief tutorial about how to repeat a command until it succeeds in Linux. local &a You have a major problem with identifying the list of files that grep is searching. Improve this question. Visit Stack Exchange If we want to rerun a command a specific number of times when it’s unsuccessful, the for loop is an ideal choice. Once the last command is successful, the loop exits. exe, the exit code is not 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 Please expand on your answer a little. Check the tries variable. Also, note that !! and !-1 will not auto-expand for you, until you execute them (when it might be too late). If using bash, you can put bind Space:magic-space into ~/. sql I want to keep repeating these psql commands in block until they all succeed. For implementation in the shell script I might use Using the command: nc 127. When all the jobs are finished, the bash should exit the while loop. retry --until=success --times=5 --delay=15 command If you need multiple commands, you can use sh -c, e. I want to run the ssh command every 5 seconds until the command succeeds. Modified 11 years, The file name is a. We’ll check the existence of the file /tmp/file using ls. How do I set a variable to the output of a command in Bash? 1419. Modified 8 years, 2 months ago. This is not plausible — I'm going to assume that you pass the list of files to be searched to the function as arguments (hence the "$@" on You can use just if curl ; then break; fi here, if you don't need the return value of curl for anything else. Could use while true; do instead. sh, and its called from the shell with the command line retry. Improve this answer. Replace "command" with the command you want to repeatedly run. In this quick tutorial, we’ll present how to perform an operation n times using different approaches. The functionality allows users to create scripts that automate repetitive tasks. If it has non 0 code it keeps going. It obviously is, so this does work in giving an endless loop. Failure in this case means a nonzero exit code, so it will only work with commands that set %errorlevel% to 0 for success or nonzero for failure. e. +1 to the answer because it's correct. It will works or not? until test-commands; do consequent-commands; done while test-commands; do consequent-commands; done for name [ [in [words As Jacob says, use the condition on the loop. The echo command prints an ASCII BEL, which will cause your terminal to emit an alert sound. Ask Question Asked 9 years, 7 months ago. We’ll retry the ls command in our examples to keep the examples simple. -c 1 will have the command only try a single ping instead of an unlimited amount of time, and -t 5 sets the timeout to 5 seconds. But [ false ] would also be always true, so a test like that is perhaps a bit misleading. trap [COMMANDS] [SIGNALS] This instructs the trap command to catch the listed SIGNALS, which may be signal names with or without the SIG prefix, or signal numbers. Then, the command should stop being run. Run the script using Bash. You can create your own repeat command doing the following steps; credits here: First, open your . Viewed 527 times If cmd1 succeeds, the whole expression will succeed, and $? will be 0. py ; do:; sleep 5m; done The above command checks, if test. Until user input equals something do - Follow up. In general, you can use the label/goto syntax in a batch file. shell command line to run a script N times. There are 3 basic loop constructs in Bash scripting, for loop, while loop, and until loop. Users can specify any executable file in the command lists. until: until Test_COMMANDS; do Block_Of_COMMANDS; done There's a built-in Unix command repeat whose first argument is the number of times to repeat a command, where the command (with any arguments) is specified by the remaining arguments to repeat. This will Magic space. In the above Bash script, the outer Bash until loop checks if the count condition is less than 1 to assign the inner until loop an asterisk variable to display asterisks that match the count variable value. In the first comment under this answer, # Ping until timeout is it possible to execute all 3 commands in a single loop but one condition, each command should execute only 1 time and also in a sequence, means second command should only execute if first completed. While using until will perpetually re-run the command until the exit code is 0 (i. Viewed 3k times 1 I want to run a command n number of times if it returns unsuccessful I have started with the below loop Repeat bash command for n seconds. For example if you forget to write sudo in front of a command, you can simply do sudo !! to run the previous command with root privileges. Also, you check the status of the web server exactly once at the startup of the script (the curl command doesn't get executed every time you Retry will run a given command repeatedly, until it is deemed an overall success of failure. Therefore, the ‘until’ loop continues to execute its block of commands until the exit status changes to ‘0’, effectively acting on failures rather than successes. Expand and execute COMMANDS as long as the final command in the 'until' COMMANDS has an exit status which is not zero. Repeat command automatically in Linux. The synopsis is timeout [options] duration command [arg]; one of the options is -k duration. Commented Aug 5, 2022 at 17:39. In this guide, we are going to learn how to repeat a command until it succeeds in Linux using BASH looping constructs:such as While loop and Until loop. – If it's a specific command you want to repeatedly execute (and not e. We assume invalid to start, trying again until meeting criteria. Keep looping if the input is invalid. Any help is always appreciated. 1 25565 < /dev/null; echo $? Netcat checks if the port is open and returns a 0 if it open, and a 1 if it closed. The tool repeats the given command until the command is successful, backing off with a configurable delay between each attempt. Ask Question Asked 11 years, 6 months ago. The loop will execute the command and if the command returns a non-zero exit code indicating an error, the loop will try again. If one of the signals is DEBUG, the list of COMMANDS is executed after every simple command. Viewed 14k times If command writes errors out to stderr, you can use the form command 2> /dev/null && echo OK || echo Failed. This code will run the [command (yes, it's a command, not syntax) and succeed because its argument is a non I want to do an 'until loop' til' the content of variable matches the pattern. My first attempt: watch -n5 ssh me@device. Begin the loop. py has completed its execution. :repeat your-command || goto :repeat echo Success! The || will only run the second command if the first one fails. Repeat bash command for n seconds. The 2> /dev/null redirects stderr output to /dev/null. g. the purpose is to show Save and close the file. Modified 1 year, 8 months ago. sql psql -U postgres -1 -f file5. It is just for notification purpose. bashrc, then pressing Space after the command will auto-expand them inline, allowing you to inspect them before execution. Ideally the way to repeat it could be piped Provided by: retry_1. Looping the code until user input succeed. Bash: Run a command repeatedly till it suceeds. If you want to search for something with a slash in it, then replace m/search/ with m#search string with /es#. While running with your given commands in the explanation I don't see anything just prompt comes again. The following script be be what you are looking for: CALL :try numTries "command and arguments" GOTO :EOF :try SET /A tries=%1 :loop IF %tries% LEQ 0 GOTO return SET /A tries-=1 EVAL %2 && (GOTO return) || (GOTO loop) :return EXIT /B . Modified 9 years, 7 months ago. If not, it keeps checking every 5 mins until we get a sys. Good luck. Example: Is there a way I can accomplish this from CLI? The retry tool will by default run the curl command over and over forever until the command returns status zero, backing off for 10 seconds between retries. Loops are handy when you want to run a series of commands over and over again until a specific condition is met. These compound commands can be Previously described examples are valid for every bash shell, but there are other solutions out there like ZSH. Have a look the the following command: This command will keep trying to ping ostechnix. Retry captures stdout into memory, and if the command was successful stdout is passed on to stdout as normal, while if the command was repeated stdout is passed to stderr instead. I think forgot to pass the exit code to the RET variable, but I get the idea. My goal is execute all the commands and in case of failure, it should retry 5 times. out a. 8 | grep timeout; then echo `say timeout`; else echo `say the internet is back up`; fi tthe original question and this answer both assume macOS. If all the jobs start running on the 100 nodes, I would like to submit new jobs and do so until all the jobs are finished. On success of the call Print a successful message or else Print the call failed. bash_aliases file: $ xdg-open ~/. If the loop exits without having managed to run cmd1 successfully, the whole expression will fail, I tried several variations on this until it dawned on me that zsh has looping capabilities itself and so right now I'm looking at if it is possible to effectively tell zsh to execute a command, and if that command fails, try that same command again but with new arguments, UNTIL the command succeeds, at which case I want the loop to end. Modified 6 years, 3 months ago. My Sample Curl would look like: curl 'https://xxxx:1234xxxx@abc. Manikandan Even if umount had output its errors on stdout, using the [command would not have made sense, because the words resulting of that output would never have made up a valid conditional expression. 8. That or running the batch file at a lower Your Do-Something should be called with the switch -ErrorAction Stop in order to issue a terminating exception that can be caught by try. edit-and-execute-command (C-x C-e) Invoke an editor on the current command line, and execute the result as shell commands. --- The construct $(ssh invalid | logger) is replaced by the stdout output of the command(s) (in this I have created a script to check and report this running every day as a cronjob, but after file2 is uploaded, it reports success every time it runs the rest of the week, is there a way to "stop running a block of code" if the script has reported success once? Here is the simple script without reporting code: Bash transforms my ping command after a successful "until loop" [duplicate] Ask Question Asked 6 years, 3 months ago. In this article, I will explore the bash until loop giving you some This is my until loop bash script that try to exec an ssh command on remote machine: n=0 until [ ${n} -ge 5 ] do ssh -oStrictHostKeyChecking=no root@test "mkdir -p /test_dir" && break something like following bash-command. Follow answered Sep 13, 2011 at 13:25 How to run command until it succeeds? 3. In the case of rsync that allow you to continue the download until it succeed :) How can you run a command in bash over and over until success? 13. Bash until Loop # The until loop is used to execute a given set of commands as long as the given condition evaluates to false. The three Bash loop constructs are for, while, and until. -k 70 is --kill-after= 70 seconds, 124 exit on timeout; what is the 60?. In this post, we’ll look at [] This presents a problem with a few bash scripts I use to automatically upload my archived backups to the SSH server, like so; So try to run the command, and check its return value. Commented Aug 1, 2020 at 22:16. Should I be doing like this: I am trying to do a CURL with an IF Else condition. For example: function DoSomething { [CmdLetBinding()] Param( ) true and false are not boolean keywords in bash; they are simply strings (and the names of commands; more on that in a moment). However, some utilities will write errors to stdout (even though this is bad practice). out is only executed if make was successful. . Perhaps a sleep command will help. If the command succeeds, the loop This trick is to use the bash while command to create a loop, but preface the command that you want to run with a ! sign so that it loops until the command succceeds. Follow answered Dec 31, 2021 at 2:16. This is easy. I'm struggling to create a bash script that monitors the web service and if is down to restart the service in a while loop until it comes back up with a 200 status response. sql psql -U postgres -1 -f file3. Keep trying until connected. r/bash Beautiful-Log5632. If the return value was not 0 (for SUCCESS) then try again. 2. However, It's not always guaranteed that the process will write to stdout again and therefore might not cause a SIGPIPE to be raised (e. STRUCTURE. And in this tutorial, I will walk you through how to use the until loop with #!/bin/bash echo begin ping if ping -c 100000 8. execute a command during every n-th iteration. py; do sleep 1 done I've seen multiple ways to automatically restart a program every x seconds, but I want to only restart the program, when it didn't run longer than x minutes. The script is using zenity. If the loop exits without having managed to run cmd1 successfully, the whole expression will fail, and $? If you just want to keep trying until the command is successful you can use the until keyword. As a special case, if a URL is given, retry will GET that URL and check for a 200 OK to be returned. Retry captures stdin into memory as the data is passed to the repeated The while and until keywords takes a command as their argument. The linked documentation does explain the command; I don't really plan to repeat it all here. make && . Start an application that writes to the Continue reading Bash trick: Repeat last command until success Assuming your script is called retry. Ask Question Asked 11 years, 10 months ago. Also, in while [ true ], the test checks if true is a non-empty string. The logic of the try sub-routine is this:. This shell has a simple built-in function for repeating a command n times: repeat 5 echo "Command" And for I want to execute a command, run for 20 hours, kill it, wait 5 seconds and repeat. Even if you fix your syntax by supplying whitespace where necessary: it is simply a non-empty string. $1, $2) within the script will be ls and foo bar. In this guide, we are going to learn how to repeat a command until it succeeds in Linux using BASH looping constructs such as While loop and Until loop. Store the number of tries into a variable. From help until. I need it to only execute once per true statement then wait until the statement is false then true again. SYNOPSIS retry [-v] [-h] [-u until] [-w while] command DESCRIPTION. it's a minimum working example, not a complete solution. The ‘ until’ loop runs as long as the condition returns a non-zero exit status. 4-1_amd64 NAME retry - Repeat command until a criteria is met, usually success. 0. SYNOPSIS retry [-v] [-h] [-u until] [-w while] command DESCRIPTION The tool repeats the given command until the command is successful, backing off with a configurable delay between each attempt. 1 done That is, you want to check the exit status of sudo/umount, not of a [command. I suggest an until loop: dropbox stop && dropbox start && until dropbox status | grep -q "Up to date"; do sleep 1; done until runs until the command returns true, that's when dropbox status output contains Up to date. Other common scenarios: Keep prompting until user types "quit" Validate form inputs match expected format ; Repeat uploading files until successful ; Carefully crafting the validation conditional is key in these cases. sh repeatcount some_command. Retry captures stdin into memory as the data is passed to the repeated command, and this captured If there are some jobs in the queue, the output on bash would indicate the number of pending jobs. An until loop works great here vs a while approach. Among various loop types such as for, while, do-while, and until, the until loop stands out for its concise approach. If the command returns a zero exit-status, signalling "success", while would run the commands in the body of the loop, while until would not run the commands in the body of the loop. Instead of waiting or running it multiple times i would like the bat file to continue its attempts until it has a success. Here’s how it works. Another mistake you did here was using -ne, which is exclusively for run command until successful n times bash. tools do this already. Retrying bash command n times and sleeping m seconds in between. This is particularly useful for history expansion from a command run a while The problem with this bit of code is it will keep executing the command while the condition is true. run command until successful n times bash. sh ls "foo bar", the positional parameters (arguments, i. It can be standard Linux Alternatively we could just initialize prev as prev=$(some_command) at the cost of running some_command an additional time at the start of the loop. : until it is a success). Loops are fundamentals of any programming language and so for the bash. Note that the point it to use the Mac's say command to report a successful ping. The execute command list will run until the last command in the condition command list fails. Sidenote: why are you using sshpass instead of public Usually to run an infinite bash loop, I do something like the following: while true; do echo test sleep 1 done What if instead, I want to do a loop that loops infinitely as long as it is How to have a bash script loop until a specific time. 2. @lexicore Since the body is not interesting for this command, we only request the head (although you could include logic to check more stuff about the state of the server). The Bash until loop takes the following form: I copy pasted your code in a new file called retry. /a. Ask Question Asked 1 year, 11 months ago. sql psql -U postgres -1 -f file2. Share. The exit status of the while and until commands is the exit status of the last command executed in list-2, or zero if none was executed. NAME. Assigning default values to Stack Exchange Network. In Bash, an exit status of ‘0’ indicates success, while any non-zero value indicates failure. My guess would If cmd1 succeeds, the whole expression will succeed, and $? will be 0. In addition retry will read from stdin once and once only, and writes to stdout once and once only, and writes all stdout to stderr if the command fails. It is a bash trick to run the previous command. In other words: Rsync / cp / or whatever command fail & close with error, so you resume it to restart (assuming you use the correct command line options which allow for resume – see below). Ok not so clear. Of course, you could use any other command here, for example to send Sometimes I restart a device and need to ssh back in when it's ready. For that, you also need to bind your function as a CmdLet. This fails until the server actually boots up. ADMIN MOD Loop until success . I often need to run different commands that would need to be re-run immediately after if the output contains a given string (status code is not enough). Once the site comes online, the While loop will end and display the "xcalc"program. retry -- sh -c 'date && false Here are a couple of examples: Reboot a server. +1 to @Earlz because he's also correct. until: until COMMANDS; do COMMANDS; done Execute commands as long as a test does not succeed. The -k duration says "if the command does not die after the SIGTERM run command until successful n times bash. sql psql -U postgres -1 -f file4. I have curl command I want to run in a loop every 10 seconds that keeps running until it is successful (exits with status 0) and echos the output to the screen. My main question is when will the until clause be evaluated? In C it won't be evaluated until after the first run of the loop, in which case my loop should work. Replace "search" with what you want to search for. Here, xcalc is optional. Using this simple bash script formula you can make a command repeat over and over until its successful: for ( i=3; i<5; i++) do execute some command 1 if command 2 is successful then do not run the command 1 (the for loop should continue) if command 2 is not successful then run command 1 only once (like retry command 1 only once, Go to bash r/bash. This is not really the same, thefuck correct spelling errors of the previous command you do. , this can happen when tailing a log file). the script tries to execute the output of the grep command and use the success/failure status of that (not the grep per se) In bash, you can use the <<< operator to redirect from a string: But if user enters wrong mysql password he receives Wrong password message and the script continues but what I want is to loop the user password attempts until it's successful and then go on with rest of the script execution. In the general case, command can be a pipeline or a list of commands; then, the exit code from the final command is the status which if will examine, similarly to how the last command in a script decides the exit status from the script. Repeat using a while loop until you succeed. A shell command to run 'x' number of times while a command keeps failing-1. Repeating an argument N times within the command line. Contribute to minfrin/retry development by creating an account on GitHub. timeout 1 bash -c 'while :; do echo check; sleep 0. Hence, it’ll be easier to create a successful or an unsuccessful trial in the examples just by creating or deleting the file. In scripting languages such as Bash, loops are useful for automating repetitive tasks. Yours is still better, though, as it allows for intermediate commands such as the sleep. The conditions and limits for what determine success/failure can be tuned with command line flags. – vschum. 4. txt, I would like to create a script that will upload a file until it is successful. I've been beating my head in over it & I'm wondering if it's even possilbe. [foo bar baz" -ne ], which would have 2 arguments (including ]) and also be falsy because bash wouldn't find the command [foo bar baz. retry - Repeat command until a criteria is met, usually success. perl -e 'do { sleep(1); $_ = `command`; print $_; } until (m/search/);' Perl is a really nice language for stuff like this. I have a sequence of psql commands in a . There are 3 basic loop I would like to define an alias that performs a command every x seconds until an underlying process gives a designated output. A little bit trickier, but you could use the timeout If you want to run a command on a Linux system until it succeeds, there are some really easy ways to do it that don’t require you to retype the command repeatedly or sit in front of your screen pressing !! (repeat the previous command) until the command works. If a signal is 0 or EXIT, the COMMANDS are executed when the shell exits. I am trying to write a bash script to loop endlessly and execute the above command every second until the output from the command equals 0 (the port opens). exit(0) from the Python code until will execute the supplied arguments as a command with arguments until the command returns true (if it returns false, it will try again). As it stands, the user types the material on standard input, and has to type Control-D to indicate EOF, then has to repeat the process for the second grep. cmd; command-prompt; The second command will run only if the first command is successful. 1; done ' 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 think forgot to pass the exit code to the RET variable, but I get the idea. Better so. Your code seems to use while and until with $?, the exit-status of the most recent command, as a command. This command will match the first successful 'pong', and then exit the next time ping tries writing to stdout. Bash scripting: If command returns nothing and user chooses to retry, repeat command. The outer loop displays the current count variable value and decrements it using count--to repeat the loop. There might be some other approach without using loop. 1. any command), you can replace "$@" in that snippet with your actual command, and name the function e. For the specific case of ping. 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. I have written the following lines of bash code The parameters for the ping command are important to get this working right. Introduction. the loop will terminate when fping returns with a 0 (success) exit code - from man fping: "Exit status is 0 if all the hosts are reachable, 1 if some hosts were unreachable, 2 if any IP addresses were not found, 3 for invalid command line arguments, and 4 for a system call failure. Also, as noted in comments, command substitution removes all trailing newlines from the command output, so if the only changes in the result are with those, this won't be able to tell the outputs If you want to run a command on a Linux system until it succeeds, there are some really easy ways to do it that don’t require you to retype the command repeatedly or sit in front of your screen pressing !! Let’s look at the two options available with bash. The following would repeat your command once/second until it is successful: until python myscript. Retry a command only once : when a command fails (in bash) 0. Alternatively, you can do this, loop until successful. The general syntax for until loop in Bash is: until <condition_command_list> do <execute_command_list> done. The until loop is handy when the condition for loop termination is less obvious or harder to Another way to tweak a previous command interactively is to use the edit-and-execute-command feature:. In this case you can omit the 2 from the redirection, but you will lose any output from the command. Bash scripting provides a set of tools for automating tasks and streamlining workflows, with loops being a key feature to execute specific tasks repetitively in a controlled manner. while . timeout 60 bash -c 'until echo > /dev/tcp/myhost/myport; do sleep 5; done' Share. com site. wsio nkvh rhyf nnbslp paks imja kku jteqn uds uunof