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0 votes

0 answers

38 views

bash subshell execution behaves unexpectedly

I have a script which is supposed to fetch 2 URLs sequentially: #!/bin/bash wget_command='wget --restrict-file-names=unix https://www.example.com/{path1,path2}/' $($wget_command) echo $wget_command >> wget_commands.log results in this message: --2025-04-30 09:13:49-- https://www.example.com/%7Bpath1...

                                  I have a script which is supposed to fetch 2 URLs sequentially:

    #!/bin/bash
    
    wget_command='wget --restrict-file-names=unix https://www.example.com/{path1,path2}/ '
    
    $($wget_command)
    
    echo $wget_command >> wget_commands.log

results in this message:

    --2025-04-30 09:13:49--  https://www.example.com/%7Bpath1,path2%7D/ 

^ the %7D is a problem

----------

Whereas, directly issuing:

    wget --restrict-file-names=unix https://www.example.com/{path1,path2}/ 

results in the expected fetches and messages:

    --2025-04-30 09:14:13--  https://www.example.com/path1/ 
    ...
    --2025-04-30 09:14:14--  https://www.example.com/path2/ 

----------

It feels like {path1,path2} is triggering an expansion/interpolation when $($wget_command) goes to use it but I am not sure how to verify nor avoid this problem.

MonkeyZeus (143 rep)

Apr 30, 2025, 01:30 PM

1 votes

0 answers

25 views

zsh - autocomplete with braces in the middle of a directory

zsh autocomplete brace-expansion

Suppose I have the following directory structure: ``` folder/ aaa/ f.txt bbb/ f.txt ``` I want to compare the file `f.txt` as it is common to both directories. So in zsh I type this: ``` % diff folder/{aaa,bbb}/ ``` Pleasingly, zsh autocompletes both the `aaa` and `bbb` directories even inside the b...

Suppose I have the following directory structure:

folder/
  aaa/
    f.txt
  bbb/
    f.txt

I want to compare the file f.txt as it is common to both directories. So in zsh I type this:

% diff folder/{aaa,bbb}/

Pleasingly, zsh autocompletes both the aaa and bbb directories even inside the brace. Next, I press the Tab key hoping that zsh will autocomplete any files common to both the aaa and bbb directories, so I'm hoping that pressing Tab will result in this:

% diff folder/{aaa,bbb}/f.txt

However, what zsh actually does is expand the braces resulting in this:

% diff folder/aaa/ folder/bbb/

My questions are: 1) Is there a zsh setting(s) to keep the braces in the middle of the directory and autocomplete the common file name as I described? 2) If not, is there a way to write a custom function to achieve this?

Trevor (1739 rep)

Mar 6, 2025, 06:19 AM • Last activity: Apr 1, 2025, 09:28 PM

9 votes

1 answers

658 views

Why does bash give the following result after brace expansion?

bash wildcards brace-expansion

I am using linux and the following version of the bash: ``` GNU bash, version 5.1.16(1)-release (x86_64-pc-linux-gnu) ``` When I type: ``` echo file{[1,2],3}.txt ``` I expect brace expansion to be done first, so: ``` echo file[1,2].txt file3.txt ``` After that, I expect it to stop there, since [1,2]...

I am using linux and the following version of the bash:

GNU bash, version 5.1.16(1)-release (x86_64-pc-linux-gnu)

When I type:

echo file{[1,2],3}.txt

I expect brace expansion to be done first, so:

echo file[1,2].txt file3.txt

After that, I expect it to stop there, since [1,2] is not a valid globbing. However, it gives the following as output:

file[1.txt file2].txt file3.txt

Why? List of files in current directory (result of ls command):

go.mod  hello.sh  hi  main.go

Yakog (517 rep)

Feb 22, 2025, 01:46 PM • Last activity: Feb 24, 2025, 12:24 PM

6 votes

2 answers

12108 views

How does curly brace expansion work in the shell?

shell command-line brace-expansion

The command `echo {1..3}-{1,2}` prints `1-1 1-2 2-1 2-2 3-1 3-2`. I understand the way those curly braces can be used. But what actually *are* they? Is it the job of `sh` / `bash` to parse/expand them and deliver the expanded version to the executed program? If so, what other tricks can it do and is...

                                  The command echo {1..3}-{1,2} prints 1-1 1-2 2-1 2-2 3-1 3-2. I understand the way those curly braces can be used. But what actually *are* they?

Is it the job of sh / bash to parse/expand them and deliver the expanded version to the executed program?

If so, what other tricks can it do and is there a specification?

Also, is there a name for it?

Is ls *.txt handled in a similar way internally?

Is there a way to achieve an n-times repetition of an argument? Like (not working, of course, only a concept): cat test.pdf{*3} ⇒ cat test.pdf test.pdf test.pdf ?

Matmarbon (265 rep)

Dec 6, 2017, 12:42 AM • Last activity: Nov 8, 2024, 01:49 AM

29 votes

2 answers

4540 views

What is the difference between `a[bc]d` (square brackets) and `a{b,c}d` (braces)?

brace-expansion pattern-matching

What is the difference between `a[bc]d` and `a{b,c}d`? Why do people use `a{b,c}d` when there is already `a[bc]d`?

                                  What is the difference between a[bc]d and a{b,c}d? Why do people use a{b,c}d when there is already a[bc]d?
                                

Weijun Zhou (3548 rep)

Apr 27, 2019, 05:35 PM • Last activity: Sep 6, 2024, 03:15 AM

2 votes

2 answers

180 views

Repeating zsh brace expansion values in zsh to download multiple files using wget2

zsh wget brace-expansion

I want to download all files named `${n}x${n}` from a directory on a website with wget2 on zsh, where `n` is the same number value both times, with n from 1 to 6000. I've found that specifying all the download URLs as arguments to a single call to `wget2` works much faster than a for loop calling `w...

I want to download all files named ${n}x${n} from a directory on a website with wget2 on zsh, where n is the same number value both times, with n from 1 to 6000. I've found that specifying all the download URLs as arguments to a single call to wget2 works much faster than a for loop calling wget2 once per URLs. I assume I could use brace expansion to populate an array, then modify the array elements to produce the correct 6,000 URLs with the number repeated, then pass the array as the arguments to wget2, but I'd prefer a more concise methodology, if possible. Maybe a one-liner with brace expansion could work. I don't know, however, how to repeat a brace expansion value. e.g.:

wget2 -q https://example.com/{1..6000}x 
# like:
#  wget2 -q https://example.com/1x1 
#  wget2 -q https://example.com/2x2 
#  …

How can I repeat a brace expansion value? Is there some other way to do this efficiently without brace expansions or without having to go through all the steps of creating an array?

XDR (451 rep)

Aug 26, 2024, 09:14 PM • Last activity: Aug 27, 2024, 09:25 AM

73 votes

7 answers

94036 views

How to create a sequence with leading zeroes using brace expansion

bash arithmetic brace-expansion

When I use the following, I get a result as expected: $ echo {8..10} 8 9 10 How can I use this brace expansion in an easy way, to get the following output? $ echo {8..10} 08 09 10 I now that this may be obtained using `seq` (didn't try), but that is not what I am looking for. Useful info may be that...

                                  When I use the following, I get a result as expected:

    $ echo {8..10}
    8 9 10

How can I use this brace expansion in an easy way, to get the following output? 

    $ echo {8..10}
    08 09 10

I now that this may be obtained using seq (didn't try), but that is not what I am looking for.

Useful info may be that I am restricted to this bash version. (If you have a zsh solution, but no bash solution, please share as well)
    
    $ bash -version
    GNU bash, version 3.2.51(1)-release (x86_64-suse-linux-gnu)

Bernhard (12573 rep)

Jan 4, 2013, 08:41 AM • Last activity: Jul 1, 2024, 01:52 PM

0 votes

1 answers

114 views

Bash brace expansion doesn't work in an export statement

bash variable brace-expansion

Consider the following example: ``` $ echo file_{a,b,c} file_a file_b file_c # brace expansion worked :) $ export VARIABLE=file_{a,b,c} $ echo $VARIABLE file_c # brace expansion didn't work :( ``` How come that if I echo `file_{a,b,c}` directly, the brace expansion prints the name of all three files...

Consider the following example:

$ echo file_{a,b,c}
file_a file_b file_c         # brace expansion worked :)

$ export VARIABLE=file_{a,b,c}
$ echo $VARIABLE
file_c                       # brace expansion didn't work :(

How come that if I echo file_{a,b,c} directly, the brace expansion prints the name of all three files, while if I assign the same expression to a variable and echo that, it only prints the name of file_c? And is there a different way to assign a brace-expanded string to a variable that would work in my case?

Thomas Fritz (185 rep)

Feb 5, 2024, 12:31 PM • Last activity: Feb 5, 2024, 01:24 PM

5 votes

4 answers

853 views

Scrabble helper in bash

grep wildcards brace-expansion

I'm trying to make a scrabble helper in bash, which when given a list of characters, finds all the words in the `/usr/share/dict/words` file. For example, when given the letters `a,c,r,t` The word `cart` will match The word `car` will also match The word `carat` will **not** match However, if `a,a,c...

                                  I'm trying to make a scrabble helper in bash, which when given a list of characters, finds all the words in the /usr/share/dict/words file.   
For example, when given the letters a,c,r,t   
The word cart will match    
The word car will also match    
The word carat will **not** match   

However, if a,a,c,r,t were given  
Then carat would have matched.

I am trying to find if it is possible only using grep, I suspect that brace expansions like        
{a,c,r,t}{a,c,r,t} might be useful to generate all the possible combinations of the letters but instead I am greeted with the errors like    

    grep: aaac: No such file or directory
    grep: aaar: No such file or directory
    grep: aaat: No such file or directory   

 
when running the command    
$ grep {a,c,r,t}{a,c,r,t}{a,c,r,t}{a,c,r,t} /usr/share/dict/words

When I use quotes like "{a,c,r,t}{a,c,r,t}" or "\{a,c,r,t\}\{a,c,r,t\}", brace expansion does not work at all

I know that the above command should not work as a scrabble helper but the errors are still rather unexpected. What is wrong with the command and how do I fix it? Also, can grep be used some way to make a scrabble helper at all?    



                                

AvZ (233 rep)

Dec 21, 2015, 08:35 AM • Last activity: Feb 2, 2024, 08:22 PM

5 votes

2 answers

9687 views

rsync: How to exclude multiple file types?

bash rsync brace-expansion

This is with bash on a Mac running Catalina: This works: ``` rsync -Pa --rsh="ssh -p 19991" --exclude '*.jpg' --exclude '*.mp4' pi@localhost:/home/pi/webcam /Volumes/Media/Webcam\ Backups/raspcondo/webcam/ ``` These do not: ``` rsync -Pa --rsh="ssh -p 19991" --exclude={'*.jpg', '*.mp4'} pi@localhost...

This is with bash on a Mac running Catalina: This works:

rsync -Pa --rsh="ssh -p 19991" --exclude '*.jpg' --exclude '*.mp4' pi@localhost:/home/pi/webcam /Volumes/Media/Webcam\ Backups/raspcondo/webcam/

These do not:

rsync -Pa --rsh="ssh -p 19991" --exclude={'*.jpg', '*.mp4'} pi@localhost:/home/pi/webcam /Volumes/Media/Webcam\ Backups/raspcondo/webcam/

rsync -Pa --rsh="ssh -p 19991" --exclude {'*.jpg', '*.mp4'} pi@localhost:/home/pi/webcam /Volumes/Media/Webcam\ Backups/raspcondo/webcam/

This is the output:

building file list ...
rsync: link_stat "/Users/mnewman/*.mp4}" failed: No such file or directory (2)
rsync: link_stat "/Users/mnewman/pi@localhost:/home/pi/webcam" failed: No such file or directory (2)
0 files to consider
sent 29 bytes  received 20 bytes  98.00 bytes/sec
total size is 0  speedup is 0.00
rsync error: some files could not be transferred (code 23) at /AppleInternal/BuildRoot/Library/Caches/com.apple.xbs/Sources/rsync/rsync-54.120.1/rsync/main.c(996) [sender=2.6.9]

What am I doing wrong with the list of file types to exclude?

Buadhai (257 rep)

May 26, 2021, 02:17 AM • Last activity: Jan 27, 2024, 03:47 AM

1 votes

1 answers

252 views

mkdir -p dir with braces created wrongly

bash directory brace-expansion mkdir

I executed the following code in Ubuntu server 16.04 xenial: mkdir -p /root/backups/{db, dirs} I recall that in another system, it worked like charm creating all 3 dirs: /root/backups/ /root/backups/db /root backup/dirs Yet this time the result was: /root/backups/ /root/backups/{db, Why is this part...

                                  I executed the following code in Ubuntu server 16.04 xenial:

    mkdir -p /root/backups/{db, dirs}

I recall that in another system, it worked like charm creating all 3 dirs:

    /root/backups/
    /root/backups/db
    /root backup/dirs

Yet this time the result was:

    /root/backups/
    /root/backups/{db,

Why is this partial, broken result?

Arcticooling (1 rep)

Jan 9, 2018, 04:35 PM • Last activity: Sep 8, 2023, 07:59 AM

0 votes

2 answers

366 views

Pass a variable that contains a comma as a -v option to qsub

bash shell environment-variables brace-expansion qsub

After seeing the reactions on [Stack Overflow](https://stackoverflow.com/questions/76616176/pass-a-variable-that-contains-a-comma-as-a-v-option-to-qsub) on this question and an unfamiliarity with qsub, I believe thqt U&L is better suited for this question. In qsub, we can pass environment variables...

info="This is some info"
qsub -v INFO=$info script.pbs

However, this becomes problematic when $info contains a comma.

info="This is some info, and here is some more!"
qsub -v INFO=$info script.pbs

This will trigger an error like so: > ERROR: -v: variable ' and here is some more!' is not set in environment variables. I have also tried encapsuling info, INFO="$info" leading to the same issue. How can I pass $info correctly, even if it contains one or more commas? The same question holds with newlines which always end up incorrectly when they are passed (backslash gets removed). Perhaps an interesting observation is that when I echo -e $info I get the output that I expect. The error is triggered in the qsub command specifically.

Bram Vanroy (183 rep)

Jul 4, 2023, 11:24 PM • Last activity: Jul 6, 2023, 07:59 AM

0 votes

2 answers

134 views

Print expression with [ ]

bash text-processing regular-expression brace-expansion

I have an input in form `A[BCDE]GT`. I would like my output to be: ABGT ACGT ADGT AEGT I have tried to use `echo`, `printf`, trying to find something that might work. Does anyone know some command that will help to execute this?

                                  I have an input in form A[BCDE]GT.
I would like my output to be:

    ABGT
    ACGT
    ADGT
    AEGT

I have tried to use echo, printf, trying to find something that might work. 
Does anyone know some command that will help to execute this?

                                

Elena (1 rep)

Apr 29, 2021, 01:36 AM • Last activity: Mar 11, 2023, 07:48 PM

9 votes

2 answers

2906 views

Append (alter) each array element via parameter expansion (i.e. without printf)?

zsh string array variable-substitution brace-expansion

Let the script below exemplify my quandary.. #!/bin/zsh STUFF=( moose-hoof ovary clydsedale ) echo ${MINE=$(printf "MY-%s " $STUFF)} echo ${MINE_EXP=${STUFF/^/MY-}} > MY-moose-hoof MY-ovary MY-clydsedale > moose-hoof ovary clydsedale What are the right expansion flags to allow string concatenation o...

                                  Let the script below exemplify my quandary..

    #!/bin/zsh

    STUFF=( moose-hoof ovary clydsedale )

    echo ${MINE=$(printf "MY-%s " $STUFF)}
    echo ${MINE_EXP=${STUFF/^/MY-}}

> MY-moose-hoof MY-ovary MY-clydsedale

> moose-hoof ovary clydsedale

What are the right expansion flags to allow string concatenation on each element of the array?

alex gray (291 rep)

Jan 31, 2016, 07:40 PM • Last activity: Jan 21, 2023, 04:33 PM

3 votes

3 answers

817 views

Brace expansion to run program multiple times with different arguments

command-line brace-expansion

I just learned about brace expansion and hoped I could make use of them to launch the same C++ program with different command line arguments. My code is run like this from the terminal: ``` mpirun -n 1 main.exe 1 10 0.1 1 5 ``` The numbers after main.exe are the input arguments of my program. I woul...

I just learned about brace expansion and hoped I could make use of them to launch the same C++ program with different command line arguments. My code is run like this from the terminal:

mpirun -n 1 main.exe 1 10 0.1 1 5

The numbers after main.exe are the input arguments of my program. I would like to do something like this:

mpirun -n 1 main.exe 1 10 {0.1,0.2} 1 5

where I expect the code to be run twice, once with 0.1 and once with 0.2 as the third argument. Why does it not work and how can I fix it? Best

reloh100 (29 rep)

Jan 9, 2023, 03:31 PM • Last activity: Jan 10, 2023, 06:46 PM

0 votes

1 answers

285 views

Bash - for range no longer works as wanted when one of the ends is a variable

bash variable-substitution brace-expansion

``` #!/bin/bash myfirstarray=(1 3 5 7 9 11) for i in {2..4} do for j in {1..${myfirstarray[$((i-1))]}} do echo ${j} done done ``` In the code above the range of the outer loop is interpreted as wanted, iterating from ```2``` to ```4```. Both substitutions in the range of the inner loop also work. Ho...

#!/bin/bash
myfirstarray=(1 3 5 7 9 11)
for i in {2..4}
	do
	for j in {1..${myfirstarray[$((i-1))]}}
		do
			echo ${j}
		done
	done

In the code above the range of the outer loop is interpreted as wanted, iterating from

. Both substitutions in the range of the inner loop also work. However the inner range is interpreted as a string and not a range of integers. How can I fix this issue? Expected:

Result:

{1..3}
{1..5}
{1..7}

wing47299 (1 rep)

Dec 19, 2022, 07:51 AM • Last activity: Dec 19, 2022, 10:50 AM

4 votes

1 answers

406 views

Why am I not able to use * with touch in path?

bash wildcards brace-expansion touch

This is the output of `tree`: ``` [xyz@localhost Semester1]$ tree . ├── Eng ├── IT ├── IT_workshop ├── LA ├── OS ├── OS_lab ├── Psy ├── Python └── Python_lab 9 directories, 0 files ``` I want to create 3 common files (named credits, links and notes) in each of these directories using `touch`. I trie...

This is the output of tree:

[xyz@localhost Semester1]$ tree
.
├── Eng
├── IT
├── IT_workshop
├── LA
├── OS
├── OS_lab
├── Psy
├── Python
└── Python_lab

9 directories, 0 files

I want to create 3 common files (named credits, links and notes) in each of these directories using touch. I tried this command: [xyz@localhost Semester1]$ touch */{credits,links,notes} and this was the output:

touch: cannot touch ‘*/credits’: No such file or directory
touch: cannot touch ‘*/links’: No such file or directory
touch: cannot touch ‘*/notes’: No such file or directory

Why did the command not work as I expected it to? BTW, I'm using CentOS Linux 7.

Random Person (311 rep)

Nov 4, 2022, 03:09 PM • Last activity: Nov 4, 2022, 05:25 PM

61 votes

7 answers

19676 views

When do you use brace expansion?

bash shell zsh ksh brace-expansion

I understand what [brace expansion][1] is, but I don't know how best to use it. When do you use it? Please teach me some convenient and remarkable examples if you have your own tip. [1]: http://www.gnu.org/software/bash/manual/bashref.html#Brace-Expansion

                                  I understand what brace expansion  is, but I don't know how best to use it.

When do you use it?  
Please teach me some convenient and remarkable examples if you have your own tip.
                                

Benjamin (1515 rep)

Jan 18, 2011, 12:34 PM • Last activity: Jun 22, 2022, 02:50 PM

8 votes

2 answers

3334 views

Avoiding non-zero exit code when running `ls` using multiple patterns

bash wildcards tcsh brace-expansion pattern-matching

Say I have two possible paths I want to list directories and files under on a Linux machine: ``` /some/path1/ /some/path2/ ``` If I do the following in `tcsh`, I get `0` exit code, if at least one of `path1` or `path2` exists: ``` ls -d /some/{path1,path2}/* ``` But if I do the exact same thing in `...

Say I have two possible paths I want to list directories and files under on a Linux machine:

/some/path1/
/some/path2/

If I do the following in tcsh, I get 0 exit code, if at least one of path1 or path2 exists:

ls -d /some/{path1,path2}/*

But if I do the exact same thing in bash, I get 2 exit code, with a stderr message reporting path1 does not exist (if path1 is the one that doesn't exist). How can I make bash behave like tcsh in this case? Is there a switch to ls that I can ask it to give back 0 if at least one path exists? If neither one exists, I do expect non-zero code, which is what tcsh gives back.

shikhanshu (245 rep)

Mar 5, 2022, 06:16 AM • Last activity: Jun 14, 2022, 03:47 PM

2 votes

1 answers

564 views

How to preserve parameter expansion passed to a function?

bash function brace-expansion

I have this function: ``` cyan=`tput setaf 6` reset=`tput sgr0` function Info() { echo "${cyan}$1${reset}" } ``` And I use it in my other scripts as simple as `Info some message`. However, when I use it to print all items of an array, it only prints the first item: ``` Info "${ArrayVariable[@]}" # t...

I have this function:

cyan=tput setaf 6
reset=tput sgr0
function Info()
{
    echo "${cyan}$1${reset}"
}

And I use it in my other scripts as simple as Info some message. However, when I use it to print all items of an array, it only prints the first item:

Info "${ArrayVariable[@]}" # this only prints the first item

echo ${ArrayVariable[@]}" # this prints all of them

How can I preserve all of the variables when using this syntax and this function?

Saeed Neamati (841 rep)

May 21, 2022, 10:19 AM • Last activity: May 21, 2022, 12:06 PM

Showing page 1 of 20 total questions