1 | #!/bin/sh
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2 |
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3 | # bash: descriptors 10 and 255
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4 | # osh: 3 and 4 taken: BAD
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5 |
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6 | # dash: 10 and 11
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7 | # mksh: 24 25 26
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8 | # zsh: 10 11 12. zsh somehow doesn't run this script correctly. It's not
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9 | # POSIX I guess.
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10 |
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11 | # count FDs greater than 10. 0-9 are reserved for scripts.
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12 | count_func() {
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13 | local count=0
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14 | local reserved=0
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15 |
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16 | local pid=$$
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17 |
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18 | # Uncomment this to show the FD table of the pipeline process! The parent
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19 | # doesn't change!
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20 |
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21 | #local pid=$BASHPID
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22 |
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23 | for path in /proc/$pid/fd/*; do
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24 | echo $path
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25 | count=$((count + 1))
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26 | local fd=$(basename $path)
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27 | if test $fd -gt 2 && test $fd -lt 10; then
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28 | reserved=$((reserved + 1))
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29 | fi
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30 | done
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31 |
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32 | ls -l /proc/$pid/fd
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33 |
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34 | echo "$count FDs open; $reserved are RESERVED (3-9)"
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35 | }
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36 |
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37 | # What does it look like inside a redirect? _tmp/err.txt must be open.
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38 | count_redir() {
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39 | {
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40 | count_func
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41 | } 2> _tmp/err.txt
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42 | }
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43 |
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44 | count_pipeline() {
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45 | count_func | cat
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46 | }
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47 |
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48 | # https://stackoverflow.com/questions/2493642/how-does-a-linux-unix-bash-script-know-its-own-pid
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49 | pid() {
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50 | echo $$ $BASHPID | cat
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51 | }
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52 |
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53 | "$@"
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54 |
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