Bash script loop not incrementing

Question

I have a script that inputs 2 -> file#.txt -> newline into my program. However, the script only inputs file4.txt into my program, even though the loop is running 10 times. I'm not sure why this is happening specifically for i=4.

gnome-terminal --working-directory=/path/to/dir/ -- bash -c "{ for i in {1..10}; 
  do echo "2"; echo "file"$i".txt"; echo $'\n'; done; } | ./program; exec bash"

Barmar · Accepted Answer · 2021-04-08 22:50:37Z

2

The $ characters are being processed by your original shell, not the shell executed inside gnome-terminal. Also, the embedded double quotes are delimiting the -c argument, not being passed explicitly to bash.

You need to escape the $ and " characters to preserve them.

gnome-terminal --working-directory=/path/to/dir/ -- bash -c "{ for i in {1..10}; 
  do echo \"2\"; echo \"file\"\$i".txt\"; echo \$'\n'; done; } | ./program; exec bash"

You could also put the command in single quotes, but then you won't be able to embed $'\n' in it, because you can't escape quotes inside single quotes. But you can use printf instead of echo, since it will translate escape sequences itself.

gnome-terminal --working-directory=/path/to/dir/ -- bash -c '{ for i in {1..10}; 
  do echo "2"; printf "file%d.txt\n\n" $i; done; } | ./program; exec bash'

See Difference between single and double quotes in Bash

answered Apr 8, 2021 at 22:50

Barmar

789k57 gold badges555 silver badges669 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Shawn Over a year ago

Or just printf "2\nfile%d.txt\n\n" {1..10} instead of a loop.

Barmar Over a year ago

@Shawn I suspect this is a simplification, and the real application may want to do more inside the loop, since this is simply printing a fixed string.

MoeMan Over a year ago

@Barmar What would I need to change if I want to pass command line arguments to my program like ./program $C1 $C2; exec bash. I had some arguments that I was passing into my program with the old command which doesn't work with the new single quotes command that I'm now using.

Barmar Over a year ago

A better approach in general would be to put everything in a script file and invoke that, rather than trying to cram it into a bash -c line.

Collectives™ on Stack Overflow

Bash script loop not incrementing

1 Answer 1

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related