29 lines
1.5 KiB
Bash
29 lines
1.5 KiB
Bash
#!/usr/bin/env bash
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normal_v="O"; null_v=""; unset unset_v
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echo -e "Pre-define: normal_v="O"; null_v=""; unset unset_v\n"
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printf "\${var:+X} normal_v:%1s null_v:%1s unset_v:%1s\n" "${normal_v:+X}" "${null_v:+X}" "${unset_v:+X}"
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printf "\${var+X} normal_v:%1s null_v:%1s unset_v:%1s\n\n" "${normal_v+X}" "${null_v+X}" "${unset_v+X}"
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printf "\${var:-X} normal_v:%1s null_v:%1s unset_v:%1s\n" "${normal_v:-X}" "${null_v:-X}" "${unset_v:-X}"
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printf "\${var-X} normal_v:%1s null_v:%1s unset_v:%1s\n\n" "${normal_v-X}" "${null_v-X}" "${unset_v-X}"
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printf "\${var:=X} normal_v:%1s null_v:%1s unset_v:%1s\n" "${normal_v:=X}" "${null_v:=X}" "${unset_v:=X}"
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printf " After normal_v=%1s null_v=%1s unset_v=%1s\n" "${normal_v}" "${null_v}" "${unset_v}"
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normal_v="O"; null_v=""; unset unset_v # reset variables
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printf "\${var=X} normal_v:%1s null_v:%1s unset_v:%1s\n" "${normal_v=X}" "${null_v=X}" "${unset_v=X}"
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printf " After normal_v=%1s null_v=%1s unset_v=%1s\n\n" "${normal_v}" "${null_v}" "${unset_v}"
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normal_v="O"; null_v=""; unset unset_v # reset variables
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printf "\${var:?X} ---\n"
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printf " normal_v : ${normal_v:?X}\n"
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printf " null_v : \${null_v:?X} # skip, or the script will be interrupted\n"
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printf " unset_v : \${unset_v:?X} # skip, or the script will be interrupted\n"
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printf "\${var?X} ---\n"
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printf " normal_v : ${normal_v?X}\n"
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printf " null_v : ${null_v?X}\n"
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printf " unset_v : \${unset_v?X} # skip, or the script will be interrupted\n"
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