I'm trying to modify some exports. I understand that this code doesn't work because its body executes in a subshell, but how do I fix it?
export | sed 's/gcc.4.2/gcc64/g' | while read line; do $line; done
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Do you want to change the export and then set the environment variable again? If yes then you have to redirect the output to another file and then source the fileRaghuram– Raghuram2012-01-12 05:30:50 +00:00Commented Jan 12, 2012 at 5:30
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@Raghuram: Yeah... is there no way to do this from within BASH?user541686– user5416862012-01-12 05:32:07 +00:00Commented Jan 12, 2012 at 5:32
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3 Answers
By arranging for the current shell to read the commands with 'process substitution':
. <(export | sed 's/gcc.4.2/gcc64/g')
Or:
source <(export | sed 's/gcc.4.2/gcc64/g')
(which is more visible, though not as succinct, as the . command).
answered Jan 12, 2012 at 5:43
Jonathan Leffler
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SiegeX
+1 although
sed -n 's/gcc.4.2/gcc64/gp' would be more efficient.Jonathan Leffler
Only setting that which needs to be set - yes, it would be more efficient. It isn't quite the same as the original, but it is in line with the intent of the original.
You can do this without the need for a temp file and I highly discourage the use of eval as you open up your system to all kinds of security problems with it.
while read -r line; do $(sed -n 's/gcc.4.2/gcc64/gp' <<<"$line"); done < <(export)
Also, by using sed -n, this only exports those entries that sed changed.
Comments
The file is probably the better solution:
export | sed 's/gcc.4.2/gcc64/g' > ~/tmp/file
. ~/tmp/file
but in case you want to avoid the creation of a temp file
eval $( export | sed 's/gcc.4.2/gcc64/; s/$/;/' )
should do the trick.
answered Jan 12, 2012 at 5:40
Diego Torres Milano
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Jonathan Leffler
This will work with other shells such as Bourne and Korn (give or take the
~ for the Bourne shell). It is probably sub-optimal for bash given the various extra tricks it has up its sleeve, notably process substitution.