pkgs/build-support/setup-hooks/shorten-perl-shebang.sh

   1 # This setup hook modifies a Perl script so that any "-I" flags in its shebang
   2 # line are rewritten into a "use lib ..." statement on the next line. This gets
   3 # around a limitation in Darwin, which will not properly handle a script whose
   4 # shebang line exceeds 511 characters.
   5 #
   6 # Each occurrence of "-I /path/to/lib1" or "-I/path/to/lib2" is removed from
   7 # the shebang line, along with the single space that preceded it. These library
   8 # paths are placed into a new line of the form
   9 #
  10 #     use lib "/path/to/lib1", "/path/to/lib2";
  11 #
  12 # immediately following the shebang line. If a library appeared in the original
  13 # list more than once, only its first occurrence will appear in the output
  14 # list. In other words, the libraries are deduplicated, but the ordering of the
  15 # first appearance of each one is preserved.
  16 #
  17 # Any flags other than "-I" in the shebang line are left as-is, and the
  18 # interpreter is also left alone (although the script will abort if the
  19 # interpreter does not seem to be either "perl" or else "env" with "perl" as
  20 # its argument). Each line after the shebang line is left unchanged. Each file
  21 # is modified in place.
  22 #
  23 # Usage:
  24 #     shortenPerlShebang SCRIPT...
  25
  26 shortenPerlShebang() {
  27     while [ $# -gt 0 ]; do
  28         _shortenPerlShebang "$1"
  29         shift
  30     done
  31 }
  32
  33 _shortenPerlShebang() {
  34     local program="$1"
  35
  36     echo "shortenPerlShebang: rewriting shebang line in $program"
  37
  38     if ! isScript "$program"; then
  39         die "shortenPerlShebang: refusing to modify $program because it is not a script"
  40     fi
  41
  42     local temp="$(mktemp)"
  43
  44     gawk '
  45         (NR == 1) {
  46             if (!($0 ~ /\/(perl|env +perl)\>/)) {
  47                 print "shortenPerlShebang: script does not seem to be a Perl script" > "/dev/stderr"
  48                 exit 1
  49             }
  50             idx = 0
  51             while (match($0, / -I ?([^ ]+)/, pieces)) {
  52                 matches[idx] = pieces[1]
  53                 idx++
  54                 $0 = gensub(/ -I ?[^ ]+/, "", 1, $0)
  55             }
  56             print $0
  57             if (idx > 0) {
  58                 prefix = "use lib "
  59                 for (idx in matches) {
  60                     path = matches[idx]
  61                     if (!(path in seen)) {
  62                         printf "%s\"%s\"", prefix, path
  63                         seen[path] = 1
  64                         prefix = ", "
  65                     }
  66                 }
  67                 print ";"
  68             }
  69         }
  70         (NR > 1 ) {
  71             print
  72         }
  73     ' "$program" > "$temp" || die
  74     # Preserve the mode of the original file
  75     cp --preserve=mode --attributes-only "$program" "$temp"
  76     mv "$temp" "$program"
  77
  78     # Measure the new shebang line length and make sure it's okay. We subtract
  79     # one to account for the trailing newline that "head" included in its
  80     # output.
  81     local new_length=$(( $(head -n 1 "$program" | wc -c) - 1 ))
  82
  83     # Darwin is okay when the shebang line contains 511 characters, but not
  84     # when it contains 512 characters.
  85     if [ $new_length -ge 512 ]; then
  86         die "shortenPerlShebang: shebang line is $new_length characters--still too long for Darwin!"
  87     fi
  88 }