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authorEuAndreh <eu@euandre.org>2025-03-31 21:51:40 -0300
committerEuAndreh <eu@euandre.org>2025-03-31 21:51:40 -0300
commit570ec471d1605318aeefb030cd78682ae442235b (patch)
tree51e17eabe37c6689f8799b55e6875c3480329a2c /src/content/tils/2021/01/17
parentMakefile, mkdeps.sh: Derive index.html and feed.xml from more static "sortdat... (diff)
downloadeuandre.org-570ec471d1605318aeefb030cd78682ae442235b.tar.gz
euandre.org-570ec471d1605318aeefb030cd78682ae442235b.tar.xz
src/content/: Update all files left to asciidoc
Diffstat (limited to 'src/content/tils/2021/01/17')
-rw-r--r--src/content/tils/2021/01/17/posix-shebang.adoc63
1 files changed, 33 insertions, 30 deletions
diff --git a/src/content/tils/2021/01/17/posix-shebang.adoc b/src/content/tils/2021/01/17/posix-shebang.adoc
index 5f5b897..4e2fbe8 100644
--- a/src/content/tils/2021/01/17/posix-shebang.adoc
+++ b/src/content/tils/2021/01/17/posix-shebang.adoc
@@ -1,55 +1,58 @@
= POSIX sh and shebangs
-date: 2021-01-17
+:awk-1: link:../../../2020/12/15/shellcheck-repo.html
+:awk-2: link:../12/curl-awk-emails.html
-layout: post
+As I {awk-1}[keep moving] {awk-2}[towards POSIX], I'm on the process of
+migrating all my Bash scripts to POSIX sh.
-lang: en
-
-ref: posix-sh-and-shebangs
-
----
-
-As I [keep moving][posix-awk-0] [towards POSIX][posix-awk-1], I'm on the process of migrating all my Bash scripts to POSIX sh.
-
-As I dropped `[[`, arrays and other Bashisms, I was left staring at the first line of every script, wondering what to do: what is the POSIX sh equivalent of `#!/usr/bin/env bash`?
-I already knew that POSIX says nothing about shebangs, and that the portable way to call a POSIX sh script is `sh script.sh`, but I didn't know what to do with that first line.
+As I dropped `[[`, arrays and other Bashisms, I was left staring at the first
+line of every script, wondering what to do: what is the POSIX sh equivalent of
+`#!/usr/bin/env bash`? I already knew that POSIX says nothing about shebangs,
+and that the portable way to call a POSIX sh script is `sh script.sh`, but
+I didn't know what to do with that first line.
What I had previously was:
-```shell
+
+[source,shell]
+----
#!/usr/bin/env bash
set -Eeuo pipefail
cd "$(dirname "${BASH_SOURCE[0]}")"
-```
+----
-Obviously, the `$BASH_SOURCE` would be gone, and I would have to adapt some of my scripts to not rely on the script location.
-The `-E` and `-o pipefail` options were also gone, and would be replaced by nothing.
+Obviously, the `$BASH_SOURCE` would be gone, and I would have to adapt some of
+my scripts to not rely on the script location. The `-E` and `-o pipefail`
+options were also gone, and would be replaced by nothing.
I converted all of them to:
-```shell
+
+[source,shell]
+----
#!/bin/sh -eu
-```
+----
I moved the `-eu` options to the shebang line itself, striving for conciseness.
-But as I changed callers from `./script.sh` to `sh script.sh`, things started to fail.
-Some tests that should fail reported errors, but didn't return 1.
+But as I changed callers from `./script.sh` to `sh script.sh`, things started to
+fail. Some tests that should fail reported errors, but didn't return 1.
-My first reaction was to revert back to `./script.sh`, but the POSIX bug I caught is a strong strain, and when I went back to it, I figured that the callers were missing some flags.
-Specifically, `sh -eu script.sh`.
+My first reaction was to revert back to `./script.sh`, but the POSIX bug I
+caught is a strong strain, and when I went back to it, I figured that the
+callers were missing some flags. Specifically, `sh -eu script.sh`.
-Then it clicked: when running with `sh script.sh`, the shebang line with the sh options is ignored, as it is a comment!
+Then it clicked: when running with `sh script.sh`, the shebang line with the sh
+options is ignored, as it is a comment!
Which means that the shebang most friendly with POSIX is:
-```shell
+[source,shell]
+----
#!/bin/sh
set -eu
-```
+----
-1. when running via `./script.sh`, if the system has an executable at `/bin/sh`, it will be used to run the script;
-2. when running via `sh script.sh`, the sh options aren't ignored as previously.
+. when running via `./script.sh`, if the system has an executable at `/bin/sh`,
+ it will be used to run the script;
+. when running via `sh script.sh`, the sh options aren't ignored as previously.
TIL.
-
-[posix-awk-0]: {% link _tils/2020-12-15-awk-snippet-shellcheck-all-scripts-in-a-repository.md %}
-[posix-awk-1]: {% link _tils/2021-01-12-awk-snippet-send-email-to-multiple-recipients-with-curl.md %}