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A good portable awk shebang is not easy to find.
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#!/usr/bin/awk -f | |
#!/usr/bin/awk -E | |
# | |
# If you have an awk version that doesn't support the -f flag, | |
# then you are just out of luck. | |
# | |
# If you just have no clue where awk will be, or you prefer to use -E, | |
# then you can try this bash snippet to launch awk for you. | |
# | |
# You might think the -E tests below are overly complex. You'd be wrong. | |
# I thank Apple for their wonderfully broken awk on Mac OS X. | |
# If you find a system, this doesn't work on please let me know! | |
# | |
# Copy the below line to the top of the file: | |
#!/usr/bin/env bash | |
# | |
# Inspired by: https://unix.stackexchange.com/a/97280 | |
# | |
_src="${0}" | |
function exec_awk() { | |
_cmd="$(command -v awk)" | |
_awk_prog="/awk:/ && /option/ && /-E/ {exit 1;} {next}" | |
_flag="-$("$_cmd" -E /dev/null </dev/null 2>&1 | "$_cmd" "$_awk_prog" && echo 'E' || echo 'f')" | |
true bash#; exec "${_cmd:-false}" "${_flag}" "${_src}" "$@"; exit; | |
} | |
true {}#; set -e; exec_awk "$@" | |
# You place your awk program below this line and make sure this file has | |
# execute permissions. |
do you actually need either -f
or -E
?
dash -c '________='\''BEGIN { for(_ in ENVIRON) { print _, length(ENVIRON[_]) } }'\'';
printf "\n\n\tawk \47%s\47\n\n" "$________"; mawk2 -- "$________" | gcat -n '
awk 'BEGIN { for(_ in ENVIRON) { print _, length(ENVIRON[_]) } }'
1 m2aCMB 37
2 mnetHnOdFn 32
….
12 HOMEBREW_PREFIX 13
13 NODE_REPL_HISTORY 30
14 mmvre1 43
15 NODE_REPL_HISTORY_SIZE 5
16 SHLVL 1
17 TMPDIR 49
18 m3rOLD 44
…….
121 ZDOTDIR 16
122 m3t 41
worked exactly the same for gawk
::::
124 # gawk profile, created Thu Jan 12 10:53:31 2023
125
126 # BEGIN rule(s)
127
128 BEGIN {
129 123 for (_ in ENVIRON) {
130 123 print _, length(ENVIRON[_])
131 }
132 }
133
in fact, if your shell allows this, directly piping in commands via /dev/stdin also works :::
dash -c ' __='\''BEGIN { for (_ in FUNCTAB) { print _, __ = FUNCTAB[_], length(_) } }'\'';
printf "%s" "$__" | gawk -p- -- "$( paste -)" | gcat -n '
1 rand rand 4
2 dcgettext dcgettext 9
3 gsub gsub 4
4 match match 5
5 int int 3
6 log log 3
7 sprintf sprintf 7
8 strftime strftime 8
9 systime systime 7
...
37 sub sub 3
38 substr substr 6
39 xor xor 3
40 lshift lshift 6
41 strtonum strtonum 8
42 toupper toupper 7
43 # gawk profile, created Thu Jan 12 11:15:06 2023
44
45 # BEGIN rule(s)
46
47 BEGIN {
48 42 for (_ in FUNCTAB) {
49 42 print _, __ = FUNCTAB[_], length(_)
50 }
51 }
52
but of course, if it supports -f
( which is just about every major awk variant actually being used) - you can even automate multi-awk code testing without needing eval or exec :
dash -c '__='\''BEGIN { srand(); srand(); OFS = "\f";
print ENVIRON["_"], ARGV[+_], srand(), NR, FPAT, OFMT, CONVFMT, ARGC, srand() }'\'';
printf "\n\n\t \"\$awkvariant\" \47%s\47\n\n" "$__";
for ___ in "nawk" "mawk" "mawk2" "gawk"; do
printf "%s" "$__" | "$___" -f- | gcat -n;
printf " %s\n\n" "$___"
done '
"$awkvariant" 'BEGIN { srand(); srand(); OFS = "\f"; print ENVIRON["_"], ARGV[+_], srand(), NR, FPAT, OFMT, CONVFMT, ARGC, srand() }'
1 /bin/dash
nawk
1673540748
0
%.6g
%.6g
1
1673540748
nawk
1 /bin/dash
mawk
1673540748
0
%.6g
%.6g
1
1673540748
mawk
1 /bin/dash
mawk2
#srand1673540748.39820#
0
%.6g
%.6g
1
#srand1673540748.39824#
mawk2
1 /bin/dash
gawk
1673540748
0
[^[:space:]]+
%.6g
%.6g
1
1673540748
gawk
The goal is to have awk
run the content of the file without introducing additional dependencies. (Using bash
is a fallback that's not preferred.)
As the comments say, if you already know where awk
will be and/or which variant of awk
will be used, and you don't care about supporting any unknown systems, then just write the shebang you need using that knowledge.
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Brilliant! Thank you.
This gist should get wider distribution. Have you considered a "self-answered" question on Stack Exchange?