acc76a6ef9
Not all systems have /bin/bash (e.g. NixOS[1] doesn't). Buildroot already uses /usr/bin/env shebangs for other interpreters (perl, python), so why not bash? This changes only the shebangs used by Buildroot itself; stuff installed to the target system is left unchanged. With this applied I can run Buildroot unmodified on NixOS. [1]: http://nixos.org/ Signed-off-by: Bjørn Forsman <bjorn.forsman@gmail.com> Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr> Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
100 lines
3.9 KiB
Bash
Executable File
100 lines
3.9 KiB
Bash
Executable File
#!/usr/bin/env bash
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# This script is a wrapper to the other download helpers.
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# Its role is to ensure atomicity when saving downloaded files
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# back to BR2_DL_DIR, and not clutter BR2_DL_DIR with partial,
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# failed downloads.
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#
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# Call it with:
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# $1: name of the helper (eg. cvs, git, cp...)
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# $2: full path to the file in which to save the download
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# $*: additional arguments to the helper in $1
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# Environment:
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# BUILD_DIR: the path to Buildroot's build dir
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# To avoid cluttering BR2_DL_DIR, we download to a trashable
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# location, namely in $(BUILD_DIR).
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# Then, we move the downloaded file to a temporary file in the
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# same directory as the final output file.
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# This allows us to finally atomically rename it to its final
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# name.
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# If anything goes wrong, we just remove all the temporaries
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# created so far.
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# We want to catch any unexpected failure, and exit immediately.
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set -e
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helper="${1}"
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output="${2}"
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shift 2
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# tmpd is a temporary directory in which helpers may store intermediate
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# by-products of the download.
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# tmpf is the file in which the helpers should put the downloaded content.
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# tmpd is located in $(BUILD_DIR), so as not to clutter the (precious)
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# $(BR2_DL_DIR)
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# We let the helpers create tmpf, so they are able to set whatever
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# permission bits they want (although we're only really interested in
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# the executable bit.)
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tmpd="$( mktemp -d "${BUILD_DIR}/.${output##*/}.XXXXXX" )"
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tmpf="${tmpd}/output"
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# Helpers expect to run in a directory that is *really* trashable, so
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# they are free to create whatever files and/or sub-dirs they might need.
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# Doing the 'cd' here rather than in all helpers is easier.
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cd "${tmpd}"
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# If the helper fails, we can just remove the temporary directory to
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# remove all the cruft it may have left behind. Then we just exit in
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# error too.
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if ! "${OLDPWD}/support/download/${helper}" "${tmpf}" "${@}"; then
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rm -rf "${tmpd}"
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exit 1
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fi
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# cd back to free the temp-dir, so we can remove it later
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cd "${OLDPWD}"
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# tmp_output is in the same directory as the final output, so we can
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# later move it atomically.
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tmp_output="$( mktemp "${output}.XXXXXX" )"
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# 'mktemp' creates files with 'go=-rwx', so the files are not accessible
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# to users other than the one doing the download (and root, of course).
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# This can be problematic when a shared BR2_DL_DIR is used by different
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# users (e.g. on a build server), where all users may write to the shared
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# location, since other users would not be allowed to read the files
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# another user downloaded.
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# So, we restore the 'go' access rights to a more sensible value, while
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# still abiding by the current user's umask. We must do that before the
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# final 'mv', so just do it now.
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# Some helpers (cp and scp) may create executable files, so we need to
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# carry the executable bit if needed.
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[ -x "${tmpf}" ] && new_mode=755 || new_mode=644
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new_mode=$( printf "%04o" $((0${new_mode} & ~0$(umask))) )
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chmod ${new_mode} "${tmp_output}"
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# We must *not* unlink tmp_output, otherwise there is a small window
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# during which another download process may create the same tmp_output
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# name (very, very unlikely; but not impossible.)
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# Using 'cp' is not reliable, since 'cp' may unlink the destination file
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# if it is unable to open it with O_WRONLY|O_TRUNC; see:
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# http://pubs.opengroup.org/onlinepubs/9699919799/utilities/cp.html
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# Since the destination filesystem can be anything, it might not support
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# O_TRUNC, so 'cp' would unlink it first.
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# Use 'cat' and append-redirection '>>' to save to the final location,
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# since that is the only way we can be 100% sure of the behaviour.
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if ! cat "${tmpf}" >>"${tmp_output}"; then
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rm -rf "${tmpd}" "${tmp_output}"
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exit 1
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fi
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rm -rf "${tmpd}"
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# tmp_output and output are on the same filesystem, so POSIX guarantees
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# that 'mv' is atomic, because it then uses rename() that POSIX mandates
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# to be atomic, see:
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# http://pubs.opengroup.org/onlinepubs/9699919799/functions/rename.html
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if ! mv "${tmp_output}" "${output}"; then
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rm -f "${tmp_output}"
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exit 1
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fi
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