Kdaj je bolje uporabiti #! / Bin / bash Namesto #! / Bin / sh v Shell Script?

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Video: Kdaj je bolje uporabiti #! / Bin / bash Namesto #! / Bin / sh v Shell Script?

Video: Kdaj je bolje uporabiti #! / Bin / bash Namesto #! / Bin / sh v Shell Script?
Video: CS50 2013 - Week 1 2024, Marec
Kdaj je bolje uporabiti #! / Bin / bash Namesto #! / Bin / sh v Shell Script?
Kdaj je bolje uporabiti #! / Bin / bash Namesto #! / Bin / sh v Shell Script?
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Pri ustvarjanju novega skripta lupine se želite prepričati, da je to čimveč problem, čeprav je morda nekoliko zmedeno, če želite vedeti, katera je najboljša za uporabo. V zvezi s tem je današnja delovna postaja SuperUser Q & A odgovor na zmedeno vprašanje bralca.
Pri ustvarjanju novega skripta lupine se želite prepričati, da je to čimveč problem, čeprav je morda nekoliko zmedeno, če želite vedeti, katera je najboljša za uporabo. V zvezi s tem je današnja delovna postaja SuperUser Q & A odgovor na zmedeno vprašanje bralca.

Današnja seja vprašanj in odgovorov se nam je zahvalila SuperUserju, ki je razdeljena na Stack Exchange, skupinsko spletno stran Q & A.

Vprašanje

Bralec SuperUserja Hendre želi vedeti, kdaj je bolje uporabljati #! / bin / bash namesto #! / bin / sh v skriptih lupine:

When is it more appropriate to use #!/bin/bash rather than #!/bin/sh in a shell script?

Kdaj je bolje uporabiti #! / bin / bash namesto #! / bin / sh v skripti lupine?

Odgovor

Odgovornost za nas:

In short:

  • There are several shells which implement a superset of the POSIX sh specification. On different systems, /bin/sh might be a link to ash, bash, dash, ksh, zsh, etc. It will always be sh-compatible though, never csh or fish.
  • As long as you stick to sh features only, you can (and probably even should) use #!/bin/sh and the script should work fine, no matter which shell it is.
  • If you start using bash-specific features (i.e. arrays), you should specifically request bash because, even if /bin/sh already invokes bash on your system, it might not on everyone else’s system, and your script will not run there. The same applies to zsh and ksh, of course.
  • Even if the script is for personal use only, you might notice that some operating systems change /bin/sh during upgrades. For example, on Debian it used to be bash, but was later replaced with the very minimal dash. Scripts which used bashisms but had #!/bin/sh suddenly broke.

However:

  • Even #!/bin/bash is not that correct. On different systems, bash might live in /usr/bin, /usr/pkg/bin, or /usr/local/bin.
  • A more reliable option is #!/usr/bin/env bash, which uses $PATH. Although the env tool itself is not strictly guaranteed either, /usr/bin/env still works on more systems than /bin/bash does.

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Kredit za slike: Wikipedia

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