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#!/usr/bin/env bash |
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# |
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# NOTE: |
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# - $! is tested in background.test.sh |
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# - $- is tested in sh-options |
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# |
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# TODO: It would be nice to make a table, like: |
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# |
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# $$ $BASHPID $PPID $SHLVL $BASH_SUBSHELL |
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# X |
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# (Subshell, Command Sub, Pipeline, Spawn $0) |
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# |
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# And see whether the variable changed. |
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|
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### $PWD |
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# Just test that it has a slash for now. |
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echo $PWD | grep -o / |
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# status: 0 |
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|
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### $1 .. $9 are scoped, while $0 is not |
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func() { echo $0 $1 $2 | sed -e 's/.*sh/sh/'; } |
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func a b |
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# stdout: sh a b |
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|
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### $? |
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echo $? # starts out as 0 |
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sh -c 'exit 33' |
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echo $? |
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# stdout-json: "0\n33\n" |
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# status: 0 |
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|
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### $# |
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set -- 1 2 3 4 |
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echo $# |
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# stdout: 4 |
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# status: 0 |
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|
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### $_ |
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# This is bash-specific. |
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echo hi |
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echo $_ |
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# stdout-json: "hi\nhi\n" |
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# N-I dash/mksh stdout-json: "hi\n\n" |
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|
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### $$ looks like a PID |
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# Just test that it has decimal digits |
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echo $$ | egrep '[0-9]+' |
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# status: 0 |
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|
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### $$ doesn't change with subshell or command sub |
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# Just test that it has decimal digits |
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set -o errexit |
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die() { |
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echo 1>&2 "$@"; exit 1 |
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} |
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parent=$$ |
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test -n "$parent" || die "empty PID in parent" |
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( child=$$ |
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test -n "$child" || die "empty PID in subshell" |
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test "$parent" = "$child" || die "should be equal: $parent != $child" |
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echo 'subshell OK' |
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) |
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echo $( child=$$ |
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test -n "$child" || die "empty PID in command sub" |
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test "$parent" = "$child" || die "should be equal: $parent != $child" |
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echo 'command sub OK' |
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) |
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exit 3 # make sure we got here |
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# status: 3 |
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## STDOUT: |
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subshell OK |
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command sub OK |
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## END |
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|
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### $BASHPID DOES change with subshell and command sub |
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set -o errexit |
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die() { |
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echo 1>&2 "$@"; exit 1 |
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} |
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parent=$BASHPID |
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test -n "$parent" || die "empty BASHPID in parent" |
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( child=$BASHPID |
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test -n "$child" || die "empty BASHPID in subshell" |
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test "$parent" != "$child" || die "should not be equal: $parent = $child" |
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echo 'subshell OK' |
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) |
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echo $( child=$BASHPID |
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test -n "$child" || die "empty BASHPID in command sub" |
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test "$parent" != "$child" || |
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die "should not be equal: $parent = $child" |
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echo 'command sub OK' |
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) |
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exit 3 # make sure we got here |
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## status: 3 |
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## STDOUT: |
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subshell OK |
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command sub OK |
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## END |
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## N-I dash status: 1 |
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## N-I dash stdout-json: "" |
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|
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### Background PID $! looks like a PID |
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sleep 0.01 & |
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pid=$! |
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wait |
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echo $pid | egrep '[0-9]+' >/dev/null |
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echo status=$? |
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# stdout: status=0 |
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|
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### $PPID |
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echo $PPID | egrep '[0-9]+' |
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# status: 0 |
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|
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# NOTE: There is also $BASHPID |
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|
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### $PIPESTATUS |
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echo hi | sh -c 'cat; exit 33' | wc -l >/dev/null |
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argv.py "${PIPESTATUS[@]}" |
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# status: 0 |
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# stdout: ['0', '33', '0'] |
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# N-I dash stdout-json: "" |
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# N-I dash status: 2 |
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|
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### $RANDOM |
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expr $0 : '.*/osh$' && exit 99 # Disabled because of spec-runner.sh issue |
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echo $RANDOM | egrep '[0-9]+' |
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# status: 0 |
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# N-I dash status: 1 |
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|
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### $UID and $EUID |
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# These are both bash-specific. |
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set -o errexit |
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echo $UID | egrep -o '[0-9]+' >/dev/null |
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echo $EUID | egrep -o '[0-9]+' >/dev/null |
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echo status=$? |
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# stdout: status=0 |
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# N-I dash/mksh stdout-json: "" |
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# N-I dash/mksh status: 1 |