[Scons-users] [Scons-dev] env.subst and variable substitution including whitespace in parameters

[RW]

Sorry I'll keep any replies to the user list,
I'm basically piping in a string from python then capturing the output and
using the results in python
so I'm capturing stdin and stdout. PSPAWN might work thanks for the info

I did also find another example where env.subst_list is useful
if you have a list of paths stored in an env variable, and those paths
contain spaces

```
env.Replace(Example1=['D:\\Temp\Test Folder 1\\src1.c'])
env.Append(Example1=['D:\\Temp\Test Folder 1\\src2.c'])
env.Append(Example1=['D:\\Temp\Test Folder 1\\src3.c'])

env.Replace(Example2=['D:\\Temp\Test Folder 1\\src4.c'])
env.Append(Example2=['D:\\Temp\Test Folder 1\\src5.c'])
env.Append(Example2=['D:\\Temp\Test Folder 1\\src6.c'])

env.Replace(SRCS='$Example1 $Example2')

# This doesn't work due to spaces in path
#items = env.Split('$SRCS')

# This results in a single string with unescaped paths
# making it difficult to split them apart or escape them
#items = env.subst('$SRCS')

items = env.subst_list('$SRCS')[0]
for item in items:
    print(item)
```

this is why I was wondering if having env.subst_list as some form of public
api should be on the github issues / todo list
to give some context, this is what the Preprocess tool I've written looks
like so far

```
def generate(env):
    env.AddMethod(PreProcessStream, 'PreProcessStream')


def PreProcessStream(env, stdin_str):
    # Handle escaping / quoting variable expansion
    escape = env.get('ESCAPE', lambda x: x)
    escape_list = SCons.Subst.escape_list

    cmdstr = '${CPP} -E ${CFLAGS} ${CCFLAGS} ${_CCCOMCOM} -'
    cmd_list = env.subst_list(cmdstr, SCons.Subst.SUBST_CMD)

    cmd_list = escape_list(cmd_list[0], escape)
    cmd = ' '.join(cmd_list)

    p = subprocess.Popen(cmd, stdout=subprocess.PIPE,
stdin=subprocess.PIPE, stderr=subprocess.PIPE)
    out, err = p.communicate(input=stdin_str.encode())
    return out, err
```

Many Thanks
Richard


On Mon, 17 Sep 2018 at 19:47, Mats Wichmann <mats at wichmann.us> wrote:

> On 09/17/2018 12:07 PM, Bill Deegan wrote:
> > Did you try having pipes in your action command string?
> > I'm thinking it should work..
> >
> > I wrote the wiki page you mentioned and it's a WIP.
>
> >> I'm wondering if this should be filed as a github issue
> >>
> >> Recently I ran into a problem, I needed to write a method to pipe some
> >> input into and out of gcc via the preprocessor
> >> this meant using subprocess instead of calling an scons Action since I
> >> wanted to do piping, but to do that I needed to expand outwards the gcc
> /
> >> cpppath etc into a string.
>
> there is some mechanism for piping in a command, see the PSPAWN
> construction environment variable.
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