These alternate forms act exactly like the normal forms, they're just a different syntax. They're slightly shorter, but less clear. Other exotic forms that exist in zsh are specific to zsh but often inspired by csh. Sign up to join this community. The best answers are voted up and rise to the top. For loops in zsh and bash Ask Question. Asked 8 years, 11 months ago. Active 8 years, 11 months ago.
Viewed k times. Does bash make a similar distinction? Addendum: Why does the following work? Amelio Vazquez-Reina Amelio Vazquez-Reina 31k 60 60 gold badges silver badges bronze badges. It is SO crazy - that those two statements - indeed do not both "work the same".
I literally can't get my head around it! I need to smoke some of what those shell designers were smoking', back in the day, lol. Careful, there is more to this story than initially appears.
I invite you to check my answer.
Re: counting in "for" loops
Active Oldest Votes. Gilles 'SO- stop being evil' Gilles 'SO- stop being evil' k gold badges silver badges bronze badges. Thanks a lot Guilles. I am still a bit confused though.
Which form is the specific one to zsh? Also, I have added one example at the end of my OP where I can't figure out how to translate between syntaxes. If the difference is just syntax, how should I fix the second script in the addendum to make it work?A simple command is a sequence of optional parameter assignments followed by blank-separated words, with optional redirections interspersed.
For a description of assignment, see the beginning of Parameters. The first word is the command to be executed, and the remaining words, if any, are arguments to the command. If a command name is given, the parameter assignments modify the environment of the command when it is executed. The value of a simple command is its exit status, or plus the signal number if terminated by a signal. For example. If job control is active, the coprocess can be treated in other than input and output as an ordinary background job.
Both operators have equal precedence and are left associative. The value of the sublist is the value of the last pipeline executed. If it does not, the value of the sublist is that return status, else it is the status returned by the print almost certainly zero. A backgrounded pipeline returns a status of zero. For example, the commands in a shell function form a special sort of list. A simple command may be preceded by a precommand modifierwhich will alter how the command is interpreted.
These modifiers are shell builtin commands with the exception of nocorrect which is a reserved word. The command word is taken to be the name of a builtin command, rather than a shell function or external command. The command word is taken to be the name of an external command, rather than a shell function or builtin. With the -v flag, command is similar to whence and with -Vit is equivalent to whence -v.
The following command together with any arguments is run in place of the current process, rather than as a sub-process. The shell does not fork and is replaced. The options are provided for compatibility with other shells. The -l option is equivalent to the - precommand modifier, to treat the replacement command as a login shell; the command is executed with a - prepended to its argv string.Apple has announced that in macOS In this series, I will document my experiences moving bash settings, configurations, and scripts over to zsh.
This series has grown into a book : reworked and expanded with more detail and topics. Like my other books, I plan to update and add to it after release as well, keeping it relevant and useful.ZSH - A Better Shell
You can order it on the Apple Books Store now. This is the final article in this series. If I ever announce an eight part series again, please somebody intervene! However, I am quite sure it will not be the last post on zsh. All the previous posts described how zsh works as an interactive shell.
The interactive shell is of course the most direct way we use a shell and configuring the shell to your taste can bring a huge boost in usefulness and productivity. The other, equally, important aspect of a shell is running script files. In the simplest perspective, script files are just series of interactive commands, but of course they will get complex very quickly.
Should you even script in zsh? The argument for bash has been that it has been pre-installed on every Mac OS X since The same is true for zshwith one exception: the zsh binary is not present on the Recovery system. It is also not present on a NetInstall or External Installation System, but these are less relevant in a modern deployment workflow, which has to work with Secure Boot Macs.
I would not consider that a future proof choice. I recommend using shellcheck to verify all your sh scripts for bash isms that might have crept in out of habit. When you can ensure your script will only run on a full macOS installation, zsh is good choice over sh.
It is pre-installed on macOS, and it offers better and safer language options than sh and some advantages over bashtoo. Deployment scripts, scripts pushed from management systems, launch daemons and launch agents, and script you write to automate your admin workflows such as building packages would fall in this category. Admins who want to keep using Python for their scripts are facing a similar problem.
Once you choose to use a non-system version of bash or pythonit is your responsibility to install and update it on all your clients. But that is what system management tools are for.Tag: zshglob. I've tried some things with find but I'd prefer to stick to pure zsh scripting if possible.
N of the pattern you use for your loop restricts the matches to plain files no directories, no symlinks, etc. Just leave it out and it will also find directories or any other file type. For more information on globbing and globbing qualifiers, have a look at man 1 zshexpn. You will also need to add the option -n to lnotherwise the symbolic links will be put into the linked directory instead of overwriting the link itself.
You misunderstand what your glob is doing. Try this with GNU find: find. The string within the braces should not change the cursor position.
Brace pairs can nest. A positive numeric argument between the Here's what your script receives: python cli. This issue fix here There appear to be two independent types of pattern matching in play here: Regular expressions: What XML Schema uses in xs:pattern. The reason for that is, that by defaultxargs gets its input from stdin but interactive applications also expect input from stdin. To prevent the One easy fix is to feed the On Enter zsh calls the accept-line widget, which causes the buffer to be executed as command.
Instead of trying to parse a file list which could be a problem when you have whitespaces or newlines in file namesI'd do the whole thing with find and its -exec filter: find. First, you create a "parameter" expansion that doesn't actually have a parameter name; it just uses the text Zsh doesn't have that option - at least, there's no mention of it in the Z Shell Manual Chapter Options.
If you see issues with your terminal after resizing the window I guess reset is always an option! So it doesn't look like there's anything built into vim to allow this. I had a play with the wrapper function and it turned out to be a little easier than I thought. Think about what happens when you run the ln -s command twice when its target is a directory rather than a file. However, if it already exists, then Note that arrays currently cannot be assigned in typeset expressions, only scalars and integers.
That means that if you type ls? There are two ways to work around that: You can make "? I ultimately ended up fetching all images from the folder and checking for each sku in the image name array.
Like TeddyKoker 's link suggested, I did the following : adding this file as exec-path-from-shell. Simple, it's exactly what the exception says: os module has no attribute path. This is because present working directory comes before library If that's the only argument that you're passing, then the rest of the glob expansion is being sucked up by the positional args part of the parsing tuple, so maybe try to use that?
Try putting an r in front of the string to make a raw string: glob. This will make it so the backslashes arent used for escaping the next character. Or, for that matter, single-quote any string literal you want to preserve as is. However, in a default zsh environment this would not be a problem, because Globbing through s of files will never being faster than having indexed those files in a database of whatever type and execute a database query for them. That's what databases are meant for.Bash loops are very useful.
In this section of our Bash Scripting Tutorial we'll look at the different loop formats available to us as well as discuss when and why you may want to use each of them.
Loops allow us to take a series of commands and keep re-running them until a particular situation is reached. They are useful for automating repetitive tasks. There are 3 basic loop structures in Bash scripting which we'll look at below. There are also a few statements which we can use to control the loops operation.
One of the easiest loops to work with is while loops. They say, while an expression is true, keep executing these lines of code. They have the following format:. You'll notice that similar to if statements the test is placed between square brackets [ ]. A common mistake is what's called an off by one error. In the example above we could have put -lt as opposed to -le less than as opposed to less than or equal.
Had we done this it would have printed up until 9. These mistakes are easy to make but also easy to fix once you've identified it so don't worry too much if you make this error. The until loop is fairly similar to the while loop. The difference is that it will execute the commands within it until the test becomes true. As you can see in the example above, the syntax is almost exactly the same as the while loop just replace while with until.
We can also create a script that does exactly the same as the while example above just by changing the test accordingly. So you may be asking, 'Why bother having the two different kinds of loops?
We don't necessarily. The while loop would be able to handle every scenario. Sometimes, however, it just makes it a little easier to read if we phrase it with until rather than while. Think about the following statement:. But they just don't seem as elegant and easy to understand. So by having both while and until we can pick whichever one makes the most sense to us and as a result, end up with code that is easier for us to understand when we read it.
We should always strive for cleanobvious and elegant code when writing our Bash scripts. The for loop is a little bit different to the previous two loops. What it does is say for each of the items in a given list, perform the given set of commands. It has the following syntax. The for loop will take each item in the list in order, one after the otherassign that item as the value of the variable varexecute the commands between do and done then go back to the top, grab the next item in the list and repeat over.
When specifying a range you may specify any number you like for both the starting value and ending value. The first value may also be larger than the second in which case it will count down. It is also possible to specify a value to increase or decrease by each time.
You do this by adding another two dots. One of the more useful applications of for loops is in the processing of a set of files. To do this we may use wildcards. Let's say we want to convert a series of.
Most of the time your loops are going to through in a smooth and ordely manner. Sometimes however we may need to intervene and alter their running slightly.Most languages have the concept of loops: If we want to repeat a task twenty times, we don't want to have to type in the code twenty times, with maybe a slight change each time.
As a result, we have for and while loops in the Bourne shell. This is somewhat fewer features than other languages, but nobody claimed that shell programming has the power of C. This is well worth trying. Make sure that you understand what is happening here. In case you don't have access to a shell at the moment it is very useful to have a shell to hand whilst reading this tutorialthe results of the above two scripts are:.
So, as you can see, for simply loops through whatever input it is given, until it runs out of input. What happens here is that the echo and read statements will run indefinitely until you type bye ; when prompted. This makes it a repeat loop, not a traditional while loop.
The colon : always evaluates to true; whilst using this can be necessary sometimes, it is often preferable to use a real exit condition. Compare quitting the above loop with the one below; see which is the more elegant. Also think of some situations in which each one would be more useful than the other:. Another useful trick is the while read f loop.
This example uses the case statement, which we'll cover later. It reads from the file myfileand for each line, tells you what human, not computer language it thinks is being used. Each line must end with a LF newline - if cat myfile doesn't end with a blank line, that final line will not be processed. For example:.
6 Shell Grammar
So make sure that you avoid typos. I recently found an old thread on Usenet which I had been involved in, where I actually learned more Google has it here. We will use while loops further in the Test and Case sections.
Note that the values can be anything at all: for2. Also think of some situations in which each one would be more useful than the other: while2. Back: 6. Escape 7. Loops Next: 8. Test LoadingToday's Posts. Quick Links.
Search Forums. Show Threads. Show Posts. Shell Programming and Scripting. Top Forums Shell Programming and Scripting a simple for loop in bash and zsh. Registered User. Join Date: Oct I am just starting to learn scripting. I am trying a simple script in bash and zsh I have two questions: First: Why zsh does not expand the var M?
What I am doing wrong? Code :. Join Date: Feb OS X Apple. MacOS Interestingly Apple has decided to switch the default shell for new users from bash to zsh in MacOS Catalina Help with simple bash script involving a loop.
Dear unix wizards, I'd be very grateful for your help with the following. I have a hypothetical file file. Run bash command inside zsh script.
Hi, I would like to run following code in bash inside a zsh script. In this case is output unfortunately very different if you run it in zsh. I tried to put "bash" in front of the code but I obtained following error message "bash: do: No such file or directory " eve though I merged the whole Help making simple perl or bash script to create a simple matrix.
Hello all! This is my first post and I'm very new to programming.