4 ms·
Not as good. I use $today a lot in file and directory names, The overhead of having to type $(today) rather than $today would be, for me, significant. I do hav
by _kst_ 8y ago
Not as good. I use $today a lot in file and directory names, The overhead of having to type $(today) rather than $today would be, for me, significant.
I do have a workaround for this particular case:
PROMPT_COMMAND='today=$(printf "%(%F)T\n" -1)'
but it only works in bash 4.2 and later.
I could use
PROMPT_COMMAND='today=$(date +%F)'
but I'm trying to avoid executing an external command on every prompt. (Maybe the overhead is low enough that it's not worth worrying about.)
My thoughts are (a) if user-defined special variables like this were a shell feature, I could find other uses for them and (b) it seems neater to make such a feature available to users rather than restricting it to three special-case built-in variables.
On the other hand, it might have been cleaner for $RANDOM, $EPOCHSECONDS, and $EPOCHREALTIME to be implemented as built-in functions rather than as special variables.
- _kst_ 8y agoI have a better (at least cleaner IMHO) workaround: PROMPT_COMMAND='printf -v today "%(%F)T" -1' printf's "-v" option was added in bash 4.0. printf's "%(...)T" format was added in bash 4.2. The "-1" argument became optional in bash 4.3. So here's what I now have in my .bashrc : if [[ "$BASH_VERSION" > "4.2" ]] ; then PROMPT_COMMAND='printf -v today "%(%F)T" -1' else PROMPT_COMMAND='today=$(date +%F)' fi (The "> 4.2" test is true for bash 4.2 and later, since the value of $BASH_VERSION for 4.2 is "4.2.0(1)-release". The ">" does a string comparison. I'll have to revisit this when and if there's a bash version 10.0, probably using $BASH_VERSINFO.)