I tried several versions but I guess I have something wrong in the syntax as I an new to linux. Improve this question. Robert Robert 1 1 gold badge 5 5 silver badges 4 4 bronze badges.
Add a comment. Active Oldest Votes. There are at least a hundred thousand million different ways of approaching this but here are the top contenders: The Bash for loop for f in. If we're just renaming doc to txt Improve this answer. Sergiy Kolodyazhnyy For the for.. Eric Carvalho Blah 2 blabla Blah 3 blabla Blah 4 blabla Blah 5 blabla Where commande is done once per line.
Reads a single line from the standard input Exit Status: The return code is zero, unless end-of-file is encountered Improve this answer. Hauri F. Hauri As xargs was initialy build for answering this kind of need, some features, like building command as long as possible in the current environment for invoking chmod in this case as less as possible, reducing forks ensure efficience.
This seem linked to Makefile specific syntax. You could try to reverse the command line: cat file. October , new edit, add interactive file processor sample.
Show 3 more comments. P k 19 19 gold badges silver badges bronze badges. Avoid one cat is a good idea, but in this case, the indicated command is xargs — F. That link doesn't seem to be relevant, perhaps the content of the web page has changed?
The rest of the answer is awesome though : — starbeamrainbowlabs. It seems page has been moved. I have re-linked and should be ok now. Thanks : — P. This was helpful, especially when you need to do something else than calling chmod i. The best way to loop over file names depends quite a bit on what you actually want to do with it, but unless you can guarantee no files have any whitespace in their name, this isn't a great way to do it. So what do you want to do in looping over the files?
Regarding the bounty : the main idea here is to get a canonical answer that covers all the possible cases filenames with new lines, problematic characters The idea is to then use these file names to do some stuff call another command, perform some renaming Don't forget that a file or a folder name can contain ". Show 2 more comments. Active Oldest Votes. The full answer: The best way depends on what you want to do, but here are a few options. Improve this answer. Gabriel Staples Kevin Kevin 50k 15 15 gold badges 96 96 silver badges bronze badges.
One xtra test e. AlexHall you can always look at the man pages man find. The latter is not only longer but also suggests that you could pass arguments containing null bytes, but you cannot.
The first null byte marks the end of the string. The first character in the empty string is the null byte that always marks the end of the string even if you don't explicitly write it down. Show 6 more comments. If a file name has any whitespace including space, tab or newline in it, it will be treated as two separate names. Although now unlikely, you can overrun your command line buffer.
Imagine if your command line buffer holds 32KB, and your for loop returns 40KB of text. That last 8KB will be dropped right off your for loop and you'll never know it.
Always use a while read construct: find. Jonathan Leffler k gold badges silver badges bronze badges. David W. It will not work with newlines in filenames. Use find's -exec instead. However, NL in file names is quite rare. Spaces in file names are quite common. The main point is not to use a for loop which many posters recommended. If you can use -exec it's better, but there are times when you really need the name given back to the shell.
For instance if you want to remove file extensions. You should use the -r option to read : -r raw input - disables interpretion of backslash escapes and line-continuation in the read data — Daira Hopwood. Note: This will put your scope into a subshell and you won't get all your variables. Show 8 more comments. Fails if newline in filename. But I adjusted my answer accordingly.
Incredibly useful on those systems that have them, though! You can use a counter to track each iteration of the loop. The use of a counter is very common in all programming languages. It can also be used to access the elements of a data structure inside the loop this is not the case for our example.
There are ways to alter the normal flow of a for loop in Bash. The two statements that allow to do that are break and continue :. Having defined a counter helps us see what happens when we add break or continue to our existing script. I will add an if statement based on the value of the counter. The break statement inside the if breaks the execution of the loop if the counter is equal to I will leave the rest of the code unchanged. So at the next iteration the value of the COUNTER is still 3 and the continue statement is executed again, and so on for all the other iterations.
If they were there the one line for loop would be a lot harder to read. If you want to learn more about loops in Bash scripting have a look at this tutorial.
I want to help you in your journey to become a Super Developer! Excellent article, very helpful, great to use as quick reminder. Thank you for it.
Every time I run a shell script I run it through shellcheck.
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