# Construct Shell Command and Run in Function
**URL:** https://discourse.julialang.org/t/construct-shell-command-and-run-in-function/24504
**Category:** New to Julia
**Created:** [May 23, 2019, 7:49am UTC](https://discourse.julialang.org/t/construct-shell-command-and-run-in-function/24504 "2019-05-23T07:49:55Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Donut\_Meepo](https://discourse.julialang.org/u/Donut_Meepo)
#### Post date: [May 23, 2019, 7:49am UTC](https://discourse.julialang.org/t/construct-shell-command-and-run-in-function/24504/1 "2019-05-23T07:49:55Z")
I am trying to construct a command out of the function arguments and run it. Here is an failed example
```julia
function display_file(fn, method)
cmd = join([method, fn], " ")
run(`$cmd`)
end
```
It seems you cannot run the whole command from interpolation
```julia
display_file("test.txt", "cat")
```
ERROR: IOError: could not spawn `‘cat test.txt’`: no such file or directory (ENOENT).
I think it is because it requires the command to be not quoted? Like, `cat ‘test.txt’` is valid.
I tried to convert the string to the cmd object by macro @cmd.
```julia
function display_file(fn, method)
cmd = join([method, fn], " ")
cmd = @cmd cmd
run(`$cmd`)
end
```
It didn’t let me make the function
ERROR: LoadError: MethodError: no method matching shell\_parse(::Symbol; special=“#{}()\<\>|&\*?~;”)
I am not very sure how the macro works. Thank you for your help.
---
### Author:  [@fredrikekre](https://discourse.julialang.org/u/fredrikekre)
#### Post date: [May 23, 2019, 8:12am UTC](https://discourse.julialang.org/t/construct-shell-command-and-run-in-function/24504/2 "2019-05-23T08:12:47Z")
`join` creates a string, and when you interpolate that into the cmd it will be quoted (as indicated by the error, note the single quotes in
```julia
could not spawn `'cat test.txt'`
```
Why do you have to use `join` at all? This works:
```julia
function display_file(fn, method)
run(`$method $fn`)
end
```
---
### Author:  [@Donut\_Meepo](https://discourse.julialang.org/u/Donut_Meepo)
#### Post date: [May 23, 2019, 8:23am UTC](https://discourse.julialang.org/t/construct-shell-command-and-run-in-function/24504/3 "2019-05-23T08:23:38Z")
Thanks for the reply.
> [@fredrikekre](#):
>
> function display\_file(fn, method) run(`$method $fn`) end
The one you suggested works on the “cat” command. Originally I was trying to do the following
```julia
display_file("https://juliacomputing.com/docs/JuliaProQuickStartGuideLinux_1.1.0.1.pdf", "wget")
```
It can start downloading without issues. But when I add parameters for wget
```julia
display_file("https://juliacomputing.com/docs/JuliaProQuickStartGuideLinux_1.1.0.1.pdf", "wget -np -nH")
```
It returns error
```julia
ERROR: IOError: could not spawn `'wget -np -nH' https://juliacomputing.com/docs/JuliaProQuickStartGuideLinux_1.1.0.1.pdf`: no such file or directory (ENOENT)
```
What should be the correct way to do it?
---
### Author:  [@fredrikekre](https://discourse.julialang.org/u/fredrikekre)
#### Post date: [May 23, 2019, 8:29am UTC](https://discourse.julialang.org/t/construct-shell-command-and-run-in-function/24504/4 "2019-05-23T08:29:04Z")
> [@Donut\_Meepo](#):
>
> “wget -np -nH”
It’s again the same issue; you input a `String` which will be quoted when you interpolate that in a cmd. Instead you can input a cmd, and interpolate that, e.g. this should work:
```julia
display_file("https://www.....pdf", `wget -np -nH`)
```
---
### Author:  [@Donut\_Meepo](https://discourse.julialang.org/u/Donut_Meepo)
#### Post date: [May 23, 2019, 8:36am UTC](https://discourse.julialang.org/t/construct-shell-command-and-run-in-function/24504/5 "2019-05-23T08:36:58Z")
Thanks a lot. That works nicely.
Just want to know a bit more to understand
```julia
display_file("https://www.....pdf", "wget")
```
Why using String “wget”, it can correctly interpolate as command?
---
### Author:  [@fredrikekre](https://discourse.julialang.org/u/fredrikekre)
#### Post date: [May 23, 2019, 8:42am UTC](https://discourse.julialang.org/t/construct-shell-command-and-run-in-function/24504/6 "2019-05-23T08:42:15Z")
Because there is nothing in the string `"wget"` that needs to be guarded with a quote, e.g. no spaces in this case.