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    ShellCheck - A shell script static analysis tool

    ShellCheck is a GPLv3 tool that gives warnings and suggestions for bash/sh shell scripts:

    Screenshot of a terminal showing problematic shell script lines highlighted

    The goals of ShellCheck are

    • To point out and clarify typical beginner's syntax issues that cause a shell to give cryptic error messages.

    • To point out and clarify typical intermediate level semantic problems that cause a shell to behave strangely and counter-intuitively.

    • To point out subtle caveats, corner cases and pitfalls that may cause an advanced user's otherwise working script to fail under future circumstances.

    See the gallery of bad code for examples of what ShellCheck can help you identify!

    Table of Contents

    How to use

    There are a number of ways to use ShellCheck!

    On the web

    Paste a shell script on https://www.shellcheck.net for instant feedback.

    ShellCheck.net is always synchronized to the latest git commit, and is the easiest way to give ShellCheck a go. Tell your friends!

    From your terminal

    Run shellcheck yourscript in your terminal for instant output, as seen above.

    In your editor

    You can see ShellCheck suggestions directly in a variety of editors.

    Screenshot of Vim showing inlined shellcheck feedback.

    Screenshot of emacs showing inlined shellcheck feedback.

    In your build or test suites

    While ShellCheck is mostly intended for interactive use, it can easily be added to builds or test suites. It makes canonical use of exit codes, so you can just add a shellcheck command as part of the process.

    For example, in a Makefile:

    check-scripts:
        # Fail if any of these files have warnings
        shellcheck myscripts/*.sh

    or in a Travis CI .travis.yml file:

    script:
      # Fail if any of these files have warnings
      - shellcheck myscripts/*.sh

    Services and platforms that have ShellCheck pre-installed and ready to use:

    Services and platforms with third party plugins:

    Most other services, including GitLab, let you install ShellCheck yourself, either through the system's package manager (see Installing), or by downloading and unpacking a binary release.

    It's a good idea to manually install a specific ShellCheck version regardless. This avoids any surprise build breaks when a new version with new warnings is published.

    For customized filtering or reporting, ShellCheck can output simple JSON, CheckStyle compatible XML, GCC compatible warnings as well as human readable text (with or without ANSI colors). See the Integration wiki page for more documentation.

    Installing

    The easiest way to install ShellCheck locally is through your package manager.

    On systems with Cabal (installs to ~/.cabal/bin):

    cabal update
    cabal install ShellCheck

    On systems with Stack (installs to ~/.local/bin):

    stack update
    stack install ShellCheck

    On Debian based distros:

    apt-get install shellcheck

    On Arch Linux based distros:

    pacman -S shellcheck

    or get the dependency free shellcheck-bin from the AUR.

    On Gentoo based distros:

    emerge --ask shellcheck

    On EPEL based distros:

    yum -y install epel-release
    yum install ShellCheck

    On Fedora based distros:

    dnf install ShellCheck

    On FreeBSD:

    pkg install hs-ShellCheck

    On macOS (OS X) with Homebrew:

    brew install shellcheck

    Or with MacPorts:

    sudo port install shellcheck

    On OpenBSD:

    pkg_add shellcheck

    On openSUSE

    zypper in ShellCheck

    Or use OneClickInstall - https://software.opensuse.org/package/ShellCheck

    On Solus:

    eopkg install shellcheck

    On Windows (via chocolatey):

    C:\> choco install shellcheck

    Or Windows (via scoop):

    C:\> scoop install shellcheck

    From conda-forge:

    conda install -c conda-forge shellcheck

    From Snap Store:

    snap install --channel=edge shellcheck

    From Docker Hub:

    docker run --rm -v "$PWD:/mnt" koalaman/shellcheck:stable myscript
    # Or :v0.4.7 for that version, or :latest for daily builds

    or use koalaman/shellcheck-alpine if you want a larger Alpine Linux based image to extend. It works exactly like a regular Alpine image, but has shellcheck preinstalled.

    Using the nix package manager:

    nix-env -iA nixpkgs.shellcheck

    Alternatively, you can download pre-compiled binaries for the latest release here:

    or see the GitHub Releases for other releases (including the latest meta-release for daily git builds).

    Distro packages already come with a man page. If you are building from source, it can be installed with:

    pandoc -s -f markdown-smart -t man shellcheck.1.md -o shellcheck.1
    sudo mv shellcheck.1 /usr/share/man/man1

    Travis CI

    Travis CI has now integrated ShellCheck by default, so you don't need to manually install it.

    If you still want to do so in order to upgrade at your leisure or ensure you're using the latest release, follow the steps below to install a binary version.

    Installing a pre-compiled binary

    The pre-compiled binaries come in tar.xz files. To decompress them, make sure xz is installed. On Debian/Ubuntu/Mint, you can apt install xz-utils. On Redhat/Fedora/CentOS, yum -y install xz.

    A simple installer may do something like:

    scversion="stable" # or "v0.4.7", or "latest"
    wget -qO- "https://github.com/koalaman/shellcheck/releases/download/${scversion?}/shellcheck-${scversion?}.linux.x86_64.tar.xz" | tar -xJv
    cp "shellcheck-${scversion}/shellcheck" /usr/bin/
    shellcheck --version

    Compiling from source

    This section describes how to build ShellCheck from a source directory. ShellCheck is written in Haskell and requires 2GB of RAM to compile.

    Installing Cabal

    ShellCheck is built and packaged using Cabal. Install the package cabal-install from your system's package manager (with e.g. apt-get, brew, emerge, yum, or zypper).

    On macOS (OS X), you can do a fast install of Cabal using brew, which takes a couple of minutes instead of more than 30 minutes if you try to compile it from source.

    $ brew install cabal-install

    On MacPorts, the package is instead called hs-cabal-install, while native Windows users should install the latest version of the Haskell platform from https://www.haskell.org/platform/

    Verify that cabal is installed and update its dependency list with

    $ cabal update

    Compiling ShellCheck

    git clone this repository, and cd to the ShellCheck source directory to build/install:

    $ cabal install

    Or if you intend to run the tests:

    $ cabal install --enable-tests

    This will compile ShellCheck and install it to your ~/.cabal/bin directory.

    Add this directory to your PATH (for bash, add this to your ~/.bashrc):

    export PATH="$HOME/.cabal/bin:$PATH"

    Log out and in again, and verify that your PATH is set up correctly:

    $ which shellcheck
    ~/.cabal/bin/shellcheck

    On native Windows, the PATH should already be set up, but the system may use a legacy codepage. In cmd.exe, powershell.exe and Powershell ISE, make sure to use a TrueType font, not a Raster font, and set the active codepage to UTF-8 (65001) with chcp:

    chcp 65001

    In Powershell ISE, you may need to additionally update the output encoding:

    [Console]::OutputEncoding = [System.Text.Encoding]::UTF8

    Running tests

    To run the unit test suite:

    $ cabal test

    Gallery of bad code

    So what kind of things does ShellCheck look for? Here is an incomplete list of detected issues.

    Quoting

    ShellCheck can recognize several types of incorrect quoting:

    echo $1                           # Unquoted variables
    find . -name *.ogg                # Unquoted find/grep patterns
    rm "~/my file.txt"                # Quoted tilde expansion
    v='--verbose="true"'; cmd $v      # Literal quotes in variables
    for f in "*.ogg"                  # Incorrectly quoted 'for' loops
    touch $@                          # Unquoted $@
    echo 'Don't forget to restart!'   # Singlequote closed by apostrophe
    echo 'Don\'t try this at home'    # Attempting to escape ' in ''
    echo 'Path is $PATH'              # Variables in single quotes
    trap "echo Took ${SECONDS}s" 0    # Prematurely expanded trap

    Conditionals

    ShellCheck can recognize many types of incorrect test statements.

    [[ n != 0 ]]                      # Constant test expressions
    [[ -e *.mpg ]]                    # Existence checks of globs
    [[ $foo==0 ]]                     # Always true due to missing spaces
    [[ -n "$foo " ]]                  # Always true due to literals
    [[ $foo =~ "fo+" ]]               # Quoted regex in =~
    [ foo =~ re ]                     # Unsupported [ ] operators
    [ $1 -eq "shellcheck" ]           # Numerical comparison of strings
    [ $n && $m ]                      # && in [ .. ]
    [ grep -q foo file ]              # Command without $(..)
    [[ "$$file" == *.jpg ]]           # Comparisons that can't succeed
    (( 1 -lt 2 ))                     # Using test operators in ((..))

    Frequently misused commands

    ShellCheck can recognize instances where commands are used incorrectly:

    grep '*foo*' file                 # Globs in regex contexts
    find . -exec foo {} && bar {} \;  # Prematurely terminated find -exec
    sudo echo 'Var=42' > /etc/profile # Redirecting sudo
    time --format=%s sleep 10         # Passing time(1) flags to time builtin
    while read h; do ssh "$h" uptime  # Commands eating while loop input
    alias archive='mv $1 /backup'     # Defining aliases with arguments
    tr -cd '[a-zA-Z0-9]'              # [] around ranges in tr
    exec foo; echo "Done!"            # Misused 'exec'
    find -name \*.bak -o -name \*~ -delete  # Implicit precedence in find
    # find . -exec foo > bar \;       # Redirections in find
    f() { whoami; }; sudo f           # External use of internal functions

    Common beginner's mistakes

    ShellCheck recognizes many common beginner's syntax errors:

    var = 42                          # Spaces around = in assignments
    $foo=42                           # $ in assignments
    for $var in *; do ...             # $ in for loop variables
    var$n="Hello"                     # Wrong indirect assignment
    echo ${var$n}                     # Wrong indirect reference
    var=(1, 2, 3)                     # Comma separated arrays
    array=( [index] = value )         # Incorrect index initialization
    echo $var[14]                     # Missing {} in array references
    echo "Argument 10 is $10"         # Positional parameter misreference
    if $(myfunction); then ..; fi     # Wrapping commands in $()
    else if othercondition; then ..   # Using 'else if'
    f; f() { echo "hello world; }     # Using function before definition
    [ false ]                         # 'false' being true
    if ( -f file )                    # Using (..) instead of test

    Style

    ShellCheck can make suggestions to improve style:

    [[ -z $(find /tmp | grep mpg) ]]  # Use grep -q instead
    a >> log; b >> log; c >> log      # Use a redirection block instead
    echo "The time is `date`"         # Use $() instead
    cd dir; process *; cd ..;         # Use subshells instead
    echo $[1+2]                       # Use standard $((..)) instead of old $[]
    echo $(($RANDOM % 6))             # Don't use $ on variables in $((..))
    echo "$(date)"                    # Useless use of echo
    cat file | grep foo               # Useless use of cat

    Data and typing errors

    ShellCheck can recognize issues related to data and typing:

    args="$@"                         # Assigning arrays to strings
    files=(foo bar); echo "$files"    # Referencing arrays as strings
    declare -A arr=(foo bar)          # Associative arrays without index
    printf "%s\n" "Arguments: $@."    # Concatenating strings and arrays
    [[ $# > 2 ]]                      # Comparing numbers as strings
    var=World; echo "Hello " var      # Unused lowercase variables
    echo "Hello $name"                # Unassigned lowercase variables
    cmd | read bar; echo $bar         # Assignments in subshells
    cat foo | cp bar                  # Piping to commands that don't read
    printf '%s: %s\n' foo             # Mismatches in printf argument count

    Robustness

    ShellCheck can make suggestions for improving the robustness of a script:

    rm -rf "$STEAMROOT/"*            # Catastrophic rm
    touch ./-l; ls *                 # Globs that could become options
    find . -exec sh -c 'a && b {}' \; # Find -exec shell injection
    printf "Hello $name"             # Variables in printf format
    for f in $(ls *.txt); do         # Iterating over ls output
    export MYVAR=$(cmd)              # Masked exit codes
    case $version in 2.*) :;; 2.6.*) # Shadowed case branches

    Portability

    ShellCheck will warn when using features not supported by the shebang. For example, if you set the shebang to #!/bin/sh, ShellCheck will warn about portability issues similar to checkbashisms:

    echo {1..$n}                     # Works in ksh, but not bash/dash/sh
    echo {1..10}                     # Works in ksh and bash, but not dash/sh
    echo -n 42                       # Works in ksh, bash and dash, undefined in sh
    trap 'exit 42' sigint            # Unportable signal spec
    cmd &> file                      # Unportable redirection operator
    read foo < /dev/tcp/host/22      # Unportable intercepted files
    foo-bar() { ..; }                # Undefined/unsupported function name
    [ $UID = 0 ]                     # Variable undefined in dash/sh
    local var=value                  # local is undefined in sh
    time sleep 1 | sleep 5           # Undefined uses of 'time'

    Miscellaneous

    ShellCheck recognizes a menagerie of other issues:

    PS1='\e[0;32m\$\e[0m '            # PS1 colors not in \[..\]
    PATH="$PATH:~/bin"                # Literal tilde in $PATH
    rm “file”                         # Unicode quotes
    echo "Hello world"                # Carriage return / DOS line endings
    echo hello \                      # Trailing spaces after \
    var=42 echo $var                  # Expansion of inlined environment
    #!/bin/bash -x -e                 # Common shebang errors
    echo $((n/180*100))               # Unnecessary loss of precision
    ls *[:digit:].txt                 # Bad character class globs
    sed 's/foo/bar/' file > file      # Redirecting to input
    while getopts "a" f; do case $f in "b") # Unhandled getopts flags

    Testimonials

    At first you're like "shellcheck is awesome" but then you're like "wtf are we still using bash"

    Alexander Tarasikov, via Twitter

    Ignoring issues

    Issues can be ignored via environmental variable, command line, individually or globally within a file:

    https://github.com/koalaman/shellcheck/wiki/Ignore

    Reporting bugs

    Please use the GitHub issue tracker for any bugs or feature suggestions:

    https://github.com/koalaman/shellcheck/issues

    Contributing

    Please submit patches to code or documentation as GitHub pull requests! Check out the DevGuide on the ShellCheck Wiki.

    Contributions must be licensed under the GNU GPLv3. The contributor retains the copyright.

    Copyright

    ShellCheck is licensed under the GNU General Public License, v3. A copy of this license is included in the file LICENSE.

    Copyright 2012-2019, Vidar 'koala_man' Holen and contributors.

    Happy ShellChecking!

    Other Resources

    • The wiki has long form descriptions for each warning, e.g. SC2221.
    • ShellCheck does not attempt to enforce any kind of formatting or indenting style, so also check out shfmt!

    项目简介

    🚀 Github 镜像仓库 🚀

    源项目地址

    https://github.com/koalaman/shellcheck

    发行版本 26

    Stable version v0.7.2

    全部发行版

    贡献者 127

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