在 docker build 期间无法使用进程替换，因为 bash 进入 posix 模式 [英] Cannot use process substitution during docker build because bash goes into posix mode

问题描述

在 Dockerfile 中，我想使用进程替换:

运行 echo <(echo '$DATA:'"$DATA")

但是 docker build 使用 /bin/sh 运行每个 RUN 命令.显然作为 sh 运行会导致 bash 切换到不允许进程替换的 POSIX 模式:

<块引用>

/bin/sh: -c: line 0: 意外标记 `(' 附近的语法错误

我尝试关闭 POSIX 模式:

RUN set +o posix &&echo <(echo '$DATA:'"$DATA")

但似乎语法错误甚至在第一个命令运行之前就发生了.如果我用 ; 替换 && 也是一样.

请注意，该命令(即使是我在此处用作简化示例的命令)同时包含单引号和双引号，因此我不能简单地添加 bash -c.

使用的shell实际上是一个bash，但是它被docker调用为/bin/sh:

<块引用>

第 7 步:运行 ls -l/bin/sh--->在 93a9809e12a7 中运行lrwxrwxrwx 1 根 9 Dec 28 03:38/bin/sh ->/bin/bash

解决方案

如果您确定正在构建的映像中有 bash，那么您可以使用 更改 shell 调用SHELL 命令，我在another question 中对此进行了描述.

您可以使用 SHELL [ "/bin/bash", "-c" ].考虑:

$ docker build --no-cache - <<(回声'>来自软呢帽>RUN cat <(echo hello world)>')将构建上下文发送到 Docker 守护进程 2.048kB步骤 1/2:来自 Fedora--->ef49352c9c21Step 2/2 : RUN cat <(echo hello world)--->在 573730ced3a3 中运行/bin/sh: -c: 第 0 行:意外标记 `(' 附近的语法错误/bin/sh: -c: line 0: `cat <(echo hello world)'命令 '/bin/sh -c cat <(echo hello world)' 返回一个非零代码:1$ docker build --no-cache - <<(回声'>来自软呢帽>外壳 ["/bin/bash", "-c"]>RUN cat <(echo hello world)>')将构建上下文发送到 Docker 守护进程 2.048kB第 1/3 步:来自 Fedora--->ef49352c9c21第 2/3 步:外壳 ["/bin/bash", "-c"]--->在 e78260e6de42 中运行移除中间容器 e78260e6de42--->ff6ec782a9f6Step 3/3 : RUN cat <(echo hello world)--->在 afbb42bba5b4 中运行你好世界移除中间容器 afbb42bba5b4--->25f756dcff9b成功搭建25f756dcff9b

In a Dockerfile, I want to use process substitution:

RUN echo <(echo '$DATA:'"$DATA")

But docker build runs every RUN command with /bin/sh. Apparently being run as sh causes bash to switch to POSIX mode, which does not allow process substitution:

/bin/sh: -c: line 0: syntax error near unexpected token `('

I tried switching off POSIX mode:

RUN set +o posix && echo <(echo '$DATA:'"$DATA")

But it seems the syntax error happens even before the first command is run. Same if I replace && with ;.

Note that the command (even the one that I used as a simplified example here) contains both single and double quotes, so I can't simply prepend bash -c.

The used shell is actually a bash, but it is invoked as /bin/sh by docker:

Step 7 : RUN ls -l /bin/sh
---> Running in 93a9809e12a7
lrwxrwxrwx    1 root     root             9 Dec 28 03:38 /bin/sh -> /bin/bash

解决方案

If you are sure you have bash in your image being built, then you can change the shell invokation by using the SHELL command, which I described in another question.

You can use SHELL [ "/bin/bash", "-c" ]. Consider:

$ docker build --no-cache - < <(echo '
> FROM fedora
> RUN cat <(echo hello world)
> ')
Sending build context to Docker daemon  2.048kB
Step 1/2 : FROM fedora
 ---> ef49352c9c21
Step 2/2 : RUN cat <(echo hello world)
 ---> Running in 573730ced3a3
/bin/sh: -c: line 0: syntax error near unexpected token `('
/bin/sh: -c: line 0: `cat <(echo hello world)'
The command '/bin/sh -c cat <(echo hello world)' returned a non-zero code: 1
$ docker build --no-cache - < <(echo '
> FROM fedora
> SHELL ["/bin/bash", "-c"]
> RUN cat <(echo hello world)
> ')
Sending build context to Docker daemon  2.048kB
Step 1/3 : FROM fedora
 ---> ef49352c9c21
Step 2/3 : SHELL ["/bin/bash", "-c"]
 ---> Running in e78260e6de42
Removing intermediate container e78260e6de42
 ---> ff6ec782a9f6
Step 3/3 : RUN cat <(echo hello world)
 ---> Running in afbb42bba5b4
hello world
Removing intermediate container afbb42bba5b4
 ---> 25f756dcff9b
Successfully built 25f756dcff9b

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