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  1. ### Please skip down to the bottom of this code
  2.  
  3. # Given a string, a separator, and a max length, shorten any segments that are
  4. # longer than the max length.
  5. shortenLongSegments() {
  6.   local -n destVar=$1; shift  # arg1: where do we write our result?
  7.   local maxLength=$1; shift   # arg2: what's the maximum length?
  8.   local IFS=$1; shift         # arg3: what character do we split into segments on?
  9.   read -r -a allSegments <<<"$1"; shift        # arg4: break into an array
  10.  
  11.   for segmentIdx in "${!allSegments[@]}"; do   # iterate over array indices
  12.     segment=${allSegments[$segmentIdx]}        # look up value for index
  13.     if (( ${#segment} > maxLength )); then     # value over maxLength chars?
  14.       segment="${segment:0:3}*${segment:${#segment}-3:3}" # build a short version
  15.       allSegments[$segmentIdx]=$segment        # store shortened version in array
  16.     fi
  17.   done
  18.   printf -v destVar '%s\n' "${allSegments[*]}" # build result string from array
  19. }
  20.  
  21. # function to call from PROMPT_COMMAND to actually build a new PS1
  22. buildNewPs1() {
  23.   # declare our locals to avoid polluting global namespace
  24.   local shorterPath
  25.   # but to cache where we last ran, we need a global; be explicit.
  26.   declare -g buildNewPs1_lastDir
  27.   # do nothing if the directory hasn't changed
  28.   [[ $PWD = "$buildNewPs1_lastDir" ]] && return 0
  29.   shortenLongSegments shorterPath 10 / "$PWD"
  30.   PS1="${shorterPath}\$"
  31.   # update the global tracking where we last ran this code
  32.   buildNewPs1_lastDir=$PWD
  33. }
  34.  
  35. sampleOne() {
  36.   PS1=`echo ${PWD#"${PWD%/*/*}/"} | awk -v RS='/' 'length()<=10{printf $0"/"}; length()>10{printf "%s*%s/", substr($0,1,3), substr($0,length()-2,3)};'| tr -d "\n"; echo "#"`
  37. }
  38. time for ((i=0; i<100; i++ )); do sampleOne; done
  39.  
  40. sampleTwo() {
  41. 	buildNewPs1
  42. }
  43. time for ((i=0; i<100; i++ )); do sampleTwo; done
Success #stdin #stdout #stderr 0.27s 5456KB
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Standard input is empty
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real	0m0.354s
user	0m0.228s
sys	0m0.035s

real	0m0.003s
user	0m0.003s
sys	0m0.000s
https://ideone.com/3ykAWR
language:
Bash (bash 5.0.3)
created:
4 years ago
visibility:
public

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