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add ability to easily download files
Signed-off-by: echohack <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,103 @@ | ||
| # These functions are the public API used by install.sh | ||
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| # Script's color palette | ||
| reset="\033[0m" | ||
| highlight="\033[42m\033[97m" | ||
| dot="\033[33m▸ $reset" | ||
| dim="\033[2m" | ||
| bold="\033[1m" | ||
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| headline() { | ||
| printf "${highlight} %s ${reset}\n" "$@" | ||
| } | ||
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| chapter() { | ||
| echo "${highlight} $((count++)).) $@ ${reset}\n" | ||
| } | ||
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| # Prints out a step, if last parameter is true then without an ending newline | ||
| step() { | ||
| if [ $# -eq 1 ] | ||
| then echo "${dot}$@" | ||
| else echo "${dot}$@" | ||
| fi | ||
| } | ||
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| run() { | ||
| echo "${dim}▹ $@ $reset" | ||
| eval $@ | ||
| } | ||
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| # Downloads a file from a source URL to a local file. | ||
| # uses an optional shasum to determine if an existing file can be used. | ||
| # | ||
| # If an existing file is present and the third argument is set with a shasum | ||
| # digest, the file will be checked to see if it's valid. If so, the function | ||
| # ends early and returns 0. Otherwise, the shasums do not match so the | ||
| # file-on-disk is removed and a normal download proceeds as though no previous | ||
| # file existed. This is designed to restart an interrupted download. | ||
| # | ||
| # Any valid `curl` URL will work. | ||
| # | ||
| # ```sh | ||
| # download_file http://example.com/file.tar.gz file.tar.gz | ||
| # # Downloads every time, even if the file exists locally | ||
| # download_file http://example.com/file.tar.gz file.tar.gz abc123... | ||
| # # Downloads if no local file is found | ||
| # download_file http://example.com/file.tar.gz file.tar.gz abc123... | ||
| # # File matches checksum: download is skipped, local file is used | ||
| # download_file http://example.com/file.tar.gz file.tar.gz oh noes... | ||
| # # File doesn't match checksum: local file removed, download attempted | ||
| # ``` | ||
| # | ||
| # Will return 0 if a file was downloaded or if a valid cached file was found. | ||
| download_file() { | ||
| local url="$1" | ||
| local dst="$HOME/Downloads/$2" | ||
| local sha="$3" | ||
| _curl_cmd=$(command -v curl) | ||
| pushd "$HOME/Downloads" > /dev/null | ||
| if [[ -f $dst && -n "$sha" ]]; then | ||
| echo "Found previous file '$dst', attempting to re-use" | ||
| if verify_file "$dst" "$sha"; then | ||
| echo "Using cached and verified '$dst'" | ||
| return 0 | ||
| else | ||
| echo "Clearing previous '$dst' file and re-attempting download" | ||
| rm -fv "$dst" | ||
| fi | ||
| fi | ||
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| echo "Downloading '$url' to '$dst'" | ||
| # shellcheck disable=2154 | ||
| $_curl_cmd -L "$url" -o "$dst" | ||
| echo "Downloaded '$dst'"; | ||
| popd > /dev/null | ||
| } | ||
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| # Verifies that a file on disk matches the given shasum. If the given shasum | ||
| # doesn't match the file's shasum then a warning is printed with the expected | ||
| # and computed shasum values. | ||
| # | ||
| # ```sh | ||
| # verify_file file.tar.gz abc123... | ||
| # ``` | ||
| # | ||
| # Will return 0 if the shasums match, and 1 if they do not match. A message | ||
| # will be printed to stderr with the expected and computed shasum values. | ||
| verify_file() { | ||
| echo "Verifying $1" | ||
| local checksum | ||
| _openssl_cmd=$(command -v openssl) | ||
| # shellcheck disable=2154 | ||
| read -r checksum _ < <($_openssl_cmd dgst -sha256 "$1" | cut -d'=' -f2) | ||
| if [[ $2 = "$checksum" ]]; then | ||
| echo "Checksum verified for $1" | ||
| else | ||
| echo "Checksum invalid for $1:" | ||
| echo " Expected: $2" | ||
| echo " Computed: ${checksum}" | ||
| return 1 | ||
| fi | ||
| return 0 | ||
| } |