Setting environment variable to a large value -> “Argument list too long”

Question

Inside a bash script, I set an environment variable to contain a string of 1 million characters. I do so like this:

export LG=XXXXXXX # ... 1 million X\'s


        

Answer 1

Command-line arguments and environment variables both come out of the same pool of space. Set environment variables too long, and you no longer have space for command-line arguments -- and even xargs, which breaks command line invocations down into smaller groupings to fit inside the pool where possible, can't operate when that pool is completely full.

So: Don't do that. For instance, you might store your data in a file, and export the path to that file in the environment.

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By the way -- the reason echo works is that it's built into your shell. Thus,

echo "$LG"

...doesn't need to start an external process, so the limits on argument list length and environment size at process startup time don't apply.

On the other hand, if you ran

/bin/echo "$LG"

...then you'd see the problem again.

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Given the explanation edited into the question as to what you're actually trying to accomplish, let me suggest an approach which requires neither environment space nor command-line space:

#!/bin/bash
#      ^-- also consider ksh; faster than bash, but also supports <()
#          /bin/sh is not usable here, as POSIX sh does not specify <().

lg=... ## DO NOT USE export HERE!
sed -f <(printf '%s\n' "s/A/$lg/g")