# Command hangs: \`run(pipeline(\`git diff\`, stderr=err, stdout=out), wait=true)\`

**URL:** <https://discourse.julialang.org/t/command-hangs-run-pipeline-git-diff-stderr-err-stdout-out-wait-true/103742>\
**Category:** General Usage\
**Tags:** shell, run, pipes\
**Created:** [September 11, 2023, 2:37pm UTC](https://discourse.julialang.org/t/command-hangs-run-pipeline-git-diff-stderr-err-stdout-out-wait-true/103742 "2023-09-11T14:37:12Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![adomasbaliuka](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/adomasbaliuka/32/29790_2.png) [@adomasbaliuka](https://discourse.julialang.org/u/adomasbaliuka)\
**Post date:** [September 11, 2023, 2:37pm UTC](https://discourse.julialang.org/t/command-hangs-run-pipeline-git-diff-stderr-err-stdout-out-wait-true/103742/1 "2023-09-11T14:37:12Z")

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(Found while debugging [DrWatson.jl](https://github.com/JuliaDynamics/DrWatson.jl/issues/300))

Setup (git repo with changed file):

```julia
# julia 1.9.3, Commit bed2cd540a1 (2023-08-24 14:43 UTC)
shell> mkdir JuliaGitWithPipeHangs
shell> cd JuliaGitWithPipeHangs
shell> git init
Initialized empty Git repository in /mnt/data/git/tmp/JuliaGitWithPipeHangs/.git/
julia> using Random; write("tmp.txt", string(rand(MersenneTwister(42), 10000)))
shell> git add tmp.txt
shell> git commit -m"commit"
julia> using Random; write("tmp.txt", string(rand(MersenneTwister(42), 100)))

```

At this point, running `git diff` in the shell works fine. Also

```julia
julia> run(`git diff`)

```

works. However, it opens a “less” view in Zshell, ~~which might be what causes the problem here:~~

```julia
julia> out = Pipe(); err = Pipe(); run(pipeline(`git diff`, stderr=err, stdout=out), wait=true)

```

This just hangs. ~~I suspect the Z-shell “less” mode is responsible. How can I make sure that it is and fix the problem? Does anyone else see this behavior?~~

 

If I open `bash` and run Julia from bash, it’s not able to run `ls` from `shell>` mode (no output), which might have to do with how the shell is configured, which I also haven’t seen before and don’t know how to fix at the moment.

~~**Edit: The problem does go away when using bash as a shell. Which leaves the question: how to make it work without changing the shell?**~~

My first instinct was to just use `LibGit2.jl` to get the diffs, however, that doesn’t seem to be possible (it can only list the changed files)?!?

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**Author:** ![savq](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/savq/32/22063_2.png) [@savq](https://discourse.julialang.org/u/savq)\
**Post date:** [September 11, 2023, 7:13pm UTC](https://discourse.julialang.org/t/command-hangs-run-pipeline-git-diff-stderr-err-stdout-out-wait-true/103742/2 "2023-09-11T19:13:37Z")

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You have a couple of misconceptions:

- Julia commands have nothing to do with your shell. `run` doesn’t “shell-out”, it spawns a child process directly.

- When you call `git diff`, it’s git (not zsh) the program that decides to use a pager.

If you don’t want to use a pager with `git`, maybe you could use the `--no-pager` option:

```sh
git --no-pager diff

```

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<div class="post-metadata">

**Author:** ![adomasbaliuka](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/adomasbaliuka/32/29790_2.png) [@adomasbaliuka](https://discourse.julialang.org/u/adomasbaliuka)\
**Post date:** [September 12, 2023, 9:09am UTC](https://discourse.julialang.org/t/command-hangs-run-pipeline-git-diff-stderr-err-stdout-out-wait-true/103742/3 "2023-09-12T09:09:50Z")

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Thanks for the help! I agree with both your points. The shell does not matter (global configurations might). Also thanks for the `--no-pager` advice.

The problem now is that **adding `--no-pager` didn’t help** and there must be another reason why the `run` call with pipes hangs. I don’t have any ideas right now…

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<div class="post-metadata">

**Author:** ![adomasbaliuka](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/adomasbaliuka/32/29790_2.png) [@adomasbaliuka](https://discourse.julialang.org/u/adomasbaliuka)\
**Post date:** [September 21, 2023, 9:05am UTC](https://discourse.julialang.org/t/command-hangs-run-pipeline-git-diff-stderr-err-stdout-out-wait-true/103742/4 "2023-09-21T09:05:43Z")

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I moved the question to [julia - Command hangs: `run(pipeline(`git --no-pager diff`, stderr=err, stdout=out), wait=true)` - Stack Overflow](https://stackoverflow.com/questions/77148743/command-hangs-runpipelinegit-no-pager-diff-stderr-err-stdout-out-wai). Please do not respond here any longer.