POSIX and Portability | shell scripts | grep -s, grep -qHow can I test for POSIX compliance of shell...

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POSIX and Portability | shell scripts | grep -s, grep -q


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.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty{ margin-bottom:0;
}







0















I am all in for portability in regards to shell scripts.



But I am unsure if I am overdoing it right now.



In this example, we have a function called confirmation, which accepts the very first argument as a string containing a question, and all of the other arguments are to be possible valid answers:





confirmation ()
{
question=$1; shift; correct_answers=$*

printf '%b' "$question\nPlease answer [ $( printf '%s' "$correct_answers" | tr ' ' / ) ] to confirm (Not <Enter>): "; read -r user_answer

# this part iterates through the list of correct answers
# and compares each as the whole word (actually as the whole line) with the user answer
for single_correct_answer in $correct_answers; do
printf '%s' "$single_correct_answer" | grep -i -x "$user_answer" > /dev/null 2>&1 && return 0
done

return 1
}

confirmation 'Do you hate me?' yes yeah kinda




As you can see, the core part is utilizing grep, so I looked into the man page, and found this:





-q, --quiet, --silent
Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. (-q is specified by POSIX .)
-s, --no-messages
Suppress error messages about nonexistent or unreadable files. Portability note: unlike GNU grep, 7th Edition Unix grep did not conform to POSIX , because it lacked -q and its -s option behaved like GNU grep's -q option. USG -style grep also lacked -q but its -s option behaved like GNU grep. Portable shell scripts should avoid both -q and -s and should redirect standard and error output to /dev/null instead. (-s is specified by POSIX .)


Let's stress this part:




Portability note: unlike GNU grep, 7th Edition Unix grep did not conform to POSIX, because it lacked -q and its -s option behaved like GNU grep's -q option. USG-style grep also lacked -q but its -s option behaved like GNU grep. Portable shell scripts should avoid both -q and -s and should redirect standard and error output to /dev/null instead.






Am I overdoing it already, or is the redirection to /dev/null the only portable way?





I am not concerned about portability to an operating system version from forty years ago!










share|improve this question

























  • Are you concerned about portability to an operating system version from forty years ago? That information is necessary and sufficient to answer your question, but you haven't provided it...

    – Michael Homer
    1 hour ago











  • @MichaelHomer added

    – Vlastimil
    30 mins ago


















0















I am all in for portability in regards to shell scripts.



But I am unsure if I am overdoing it right now.



In this example, we have a function called confirmation, which accepts the very first argument as a string containing a question, and all of the other arguments are to be possible valid answers:





confirmation ()
{
question=$1; shift; correct_answers=$*

printf '%b' "$question\nPlease answer [ $( printf '%s' "$correct_answers" | tr ' ' / ) ] to confirm (Not <Enter>): "; read -r user_answer

# this part iterates through the list of correct answers
# and compares each as the whole word (actually as the whole line) with the user answer
for single_correct_answer in $correct_answers; do
printf '%s' "$single_correct_answer" | grep -i -x "$user_answer" > /dev/null 2>&1 && return 0
done

return 1
}

confirmation 'Do you hate me?' yes yeah kinda




As you can see, the core part is utilizing grep, so I looked into the man page, and found this:





-q, --quiet, --silent
Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. (-q is specified by POSIX .)
-s, --no-messages
Suppress error messages about nonexistent or unreadable files. Portability note: unlike GNU grep, 7th Edition Unix grep did not conform to POSIX , because it lacked -q and its -s option behaved like GNU grep's -q option. USG -style grep also lacked -q but its -s option behaved like GNU grep. Portable shell scripts should avoid both -q and -s and should redirect standard and error output to /dev/null instead. (-s is specified by POSIX .)


Let's stress this part:




Portability note: unlike GNU grep, 7th Edition Unix grep did not conform to POSIX, because it lacked -q and its -s option behaved like GNU grep's -q option. USG-style grep also lacked -q but its -s option behaved like GNU grep. Portable shell scripts should avoid both -q and -s and should redirect standard and error output to /dev/null instead.






Am I overdoing it already, or is the redirection to /dev/null the only portable way?





I am not concerned about portability to an operating system version from forty years ago!










share|improve this question

























  • Are you concerned about portability to an operating system version from forty years ago? That information is necessary and sufficient to answer your question, but you haven't provided it...

    – Michael Homer
    1 hour ago











  • @MichaelHomer added

    – Vlastimil
    30 mins ago














0












0








0








I am all in for portability in regards to shell scripts.



But I am unsure if I am overdoing it right now.



In this example, we have a function called confirmation, which accepts the very first argument as a string containing a question, and all of the other arguments are to be possible valid answers:





confirmation ()
{
question=$1; shift; correct_answers=$*

printf '%b' "$question\nPlease answer [ $( printf '%s' "$correct_answers" | tr ' ' / ) ] to confirm (Not <Enter>): "; read -r user_answer

# this part iterates through the list of correct answers
# and compares each as the whole word (actually as the whole line) with the user answer
for single_correct_answer in $correct_answers; do
printf '%s' "$single_correct_answer" | grep -i -x "$user_answer" > /dev/null 2>&1 && return 0
done

return 1
}

confirmation 'Do you hate me?' yes yeah kinda




As you can see, the core part is utilizing grep, so I looked into the man page, and found this:





-q, --quiet, --silent
Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. (-q is specified by POSIX .)
-s, --no-messages
Suppress error messages about nonexistent or unreadable files. Portability note: unlike GNU grep, 7th Edition Unix grep did not conform to POSIX , because it lacked -q and its -s option behaved like GNU grep's -q option. USG -style grep also lacked -q but its -s option behaved like GNU grep. Portable shell scripts should avoid both -q and -s and should redirect standard and error output to /dev/null instead. (-s is specified by POSIX .)


Let's stress this part:




Portability note: unlike GNU grep, 7th Edition Unix grep did not conform to POSIX, because it lacked -q and its -s option behaved like GNU grep's -q option. USG-style grep also lacked -q but its -s option behaved like GNU grep. Portable shell scripts should avoid both -q and -s and should redirect standard and error output to /dev/null instead.






Am I overdoing it already, or is the redirection to /dev/null the only portable way?





I am not concerned about portability to an operating system version from forty years ago!










share|improve this question
















I am all in for portability in regards to shell scripts.



But I am unsure if I am overdoing it right now.



In this example, we have a function called confirmation, which accepts the very first argument as a string containing a question, and all of the other arguments are to be possible valid answers:





confirmation ()
{
question=$1; shift; correct_answers=$*

printf '%b' "$question\nPlease answer [ $( printf '%s' "$correct_answers" | tr ' ' / ) ] to confirm (Not <Enter>): "; read -r user_answer

# this part iterates through the list of correct answers
# and compares each as the whole word (actually as the whole line) with the user answer
for single_correct_answer in $correct_answers; do
printf '%s' "$single_correct_answer" | grep -i -x "$user_answer" > /dev/null 2>&1 && return 0
done

return 1
}

confirmation 'Do you hate me?' yes yeah kinda




As you can see, the core part is utilizing grep, so I looked into the man page, and found this:





-q, --quiet, --silent
Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. (-q is specified by POSIX .)
-s, --no-messages
Suppress error messages about nonexistent or unreadable files. Portability note: unlike GNU grep, 7th Edition Unix grep did not conform to POSIX , because it lacked -q and its -s option behaved like GNU grep's -q option. USG -style grep also lacked -q but its -s option behaved like GNU grep. Portable shell scripts should avoid both -q and -s and should redirect standard and error output to /dev/null instead. (-s is specified by POSIX .)


Let's stress this part:




Portability note: unlike GNU grep, 7th Edition Unix grep did not conform to POSIX, because it lacked -q and its -s option behaved like GNU grep's -q option. USG-style grep also lacked -q but its -s option behaved like GNU grep. Portable shell scripts should avoid both -q and -s and should redirect standard and error output to /dev/null instead.






Am I overdoing it already, or is the redirection to /dev/null the only portable way?





I am not concerned about portability to an operating system version from forty years ago!







shell-script grep scripting posix portability






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 30 mins ago







Vlastimil

















asked 2 hours ago









VlastimilVlastimil

8,7691768153




8,7691768153













  • Are you concerned about portability to an operating system version from forty years ago? That information is necessary and sufficient to answer your question, but you haven't provided it...

    – Michael Homer
    1 hour ago











  • @MichaelHomer added

    – Vlastimil
    30 mins ago



















  • Are you concerned about portability to an operating system version from forty years ago? That information is necessary and sufficient to answer your question, but you haven't provided it...

    – Michael Homer
    1 hour ago











  • @MichaelHomer added

    – Vlastimil
    30 mins ago

















Are you concerned about portability to an operating system version from forty years ago? That information is necessary and sufficient to answer your question, but you haven't provided it...

– Michael Homer
1 hour ago





Are you concerned about portability to an operating system version from forty years ago? That information is necessary and sufficient to answer your question, but you haven't provided it...

– Michael Homer
1 hour ago













@MichaelHomer added

– Vlastimil
30 mins ago





@MichaelHomer added

– Vlastimil
30 mins ago










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