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| 1 | +#!/usr/bin/env bash |
| 2 | +# |
| 3 | +# Verify the checksum of a file. |
| 4 | +# |
| 5 | +# Usage: checksum <filepath> <hash> |
| 6 | +# |
| 7 | +# Arguments: |
| 8 | +# |
| 9 | +# filepath File to verify. |
| 10 | +# hash Expected checksum. |
| 11 | +# |
| 12 | + |
| 13 | +# VARIABLES # |
| 14 | + |
| 15 | +# Checksum type: |
| 16 | +checksum_type='sha256' |
| 17 | + |
| 18 | +# Program used to compute a checksum: |
| 19 | +checksum_program= |
| 20 | + |
| 21 | +# File to verify: |
| 22 | +file= |
| 23 | + |
| 24 | +# Command to compute a checksum: |
| 25 | +cmd= |
| 26 | + |
| 27 | +# Expected checksum: |
| 28 | +expected_checksum= |
| 29 | + |
| 30 | +# Actual checksum: |
| 31 | +curr_checksum= |
| 32 | + |
| 33 | + |
| 34 | +# FUNCTIONS # |
| 35 | + |
| 36 | +# Prints usage information. |
| 37 | +usage() { |
| 38 | + echo '' >&2 |
| 39 | + echo 'Usage: checksum <filepath> <hash>' >&2 |
| 40 | + echo '' >&2 |
| 41 | +} |
| 42 | + |
| 43 | +# Prints a success message. |
| 44 | +print_success() { |
| 45 | + echo 'Success.' >&2 |
| 46 | +} |
| 47 | + |
| 48 | +# Prints a checksum. |
| 49 | +# |
| 50 | +# $1 - checksum |
| 51 | +print_checksum() { |
| 52 | + local num_lines |
| 53 | + local width |
| 54 | + local lines |
| 55 | + local len |
| 56 | + local pos |
| 57 | + |
| 58 | + width=64 # characters |
| 59 | + len="${#1}" |
| 60 | + if [[ "${len}" -gt "${width}" ]]; then |
| 61 | + num_lines=$(("${len}" / "${width}")) # floored |
| 62 | + lines=$(seq 0 1 "${num_lines}") # total_lines = num_lines + 1 |
| 63 | + for i in "${lines}"; do |
| 64 | + pos=$((i * "${width}")) |
| 65 | + echo " ${str:${pos}:${width}}" |
| 66 | + done |
| 67 | + else |
| 68 | + echo " $1" >&2 |
| 69 | + fi |
| 70 | +} |
| 71 | + |
| 72 | +# Prints a checksum error. |
| 73 | +# |
| 74 | +# $1 - file |
| 75 | +# $2 - checksum type |
| 76 | +# $3 - checksum program |
| 77 | +# $4 - expected checksum |
| 78 | +# $5 - actual checksum |
| 79 | +print_checksum_error() { |
| 80 | + echo '' >&2 |
| 81 | + echo "ERROR: $2 checksum failure for $1. Expected:" >&2 |
| 82 | + echo '' >&2 |
| 83 | + print_checksum "$4" |
| 84 | + echo '' >&2 |
| 85 | + echo "But \`$3\` results in:" >&2 |
| 86 | + echo '' >&2 |
| 87 | + print_checksum "$5" |
| 88 | + echo '' >&2 |
| 89 | + echo "This may be due to bad downloads or network proxies. Check your network proxy/" >&2 |
| 90 | + echo "firewall settings and try downloading and verifying again." >&2 |
| 91 | + echo '' >&2 |
| 92 | +} |
| 93 | + |
| 94 | + |
| 95 | +# MAIN # |
| 96 | + |
| 97 | +# Handle arguments... |
| 98 | +if [[ "$#" -eq 0 ]]; then |
| 99 | + usage |
| 100 | + exit 0 |
| 101 | +elif [[ "$#" -eq 2 ]]; then |
| 102 | + file="$1" |
| 103 | + expected_checksum="$2" |
| 104 | +else |
| 105 | + echo 'ERROR: unrecognized arguments. Must provide a file to verify and an expected checksum.' >&2 |
| 106 | + exit 1 |
| 107 | +fi |
| 108 | + |
| 109 | +# Find a program for computing a SHA256 checksum... |
| 110 | +if [[ -n "$(which sha256sum)" ]]; then |
| 111 | + checksum_program="sha256sum" |
| 112 | + cmd="sha256sum ${file} | awk '{ print \$1; }'" |
| 113 | +elif [[ -n "$(which shasum)" ]]; then |
| 114 | + checksum_program="shasum" |
| 115 | + cmd="shasum -a 256 ${file} | awk '{ print \$1; }'" |
| 116 | +fi |
| 117 | + |
| 118 | +# Verify checksum: |
| 119 | +curr_checksum=$(eval "${cmd}") |
| 120 | + |
| 121 | +if [[ "${curr_checksum}" != "${expected_checksum}" ]]; then |
| 122 | + print_checksum_error "${file}" "${checksum_type}" "${checksum_program}" "${expected_checksum}" "${curr_checksum}" |
| 123 | + exit 1 |
| 124 | +else |
| 125 | + print_success |
| 126 | + exit 0 |
| 127 | +fi |
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