ShellCheck SC1xxx Rules (Source Code Issues)

bashrs implements 60 SC1xxx rules covering source-level shell script issues: shebang problems, quoting mistakes, spacing errors, syntax style, here-document issues, unicode encoding problems, portability concerns, and source/include warnings.

These rules detect issues that occur before the shell even begins interpreting the script -- encoding problems, syntax mistakes, and common typos that prevent correct parsing.

Rule Categories

Shebang Rules

SC1084: Use #! not !#

Severity: Error

Detects reversed shebang where !# is used instead of #!.

 Bad:
!#/bin/bash
echo "hello"

 Good:
!/bin/bash
echo "hello"

SC1113: Use #! not just #

Severity: Warning

Detects shebang missing the ! character.

 Bad:
 /bin/sh
echo "hello"

 Good:
!/bin/sh
echo "hello"

SC1114: Leading spaces before shebang

Severity: Warning

Shebang must be the very first characters of the file.

 Bad:
  !/bin/sh
echo "hello"

 Good:
!/bin/sh
echo "hello"

SC1115: Space between # and !

Severity: Warning

Detects # ! instead of #!.

SC1127: Use # for comments, not //

Severity: Warning

Detects C/C++ style comments that will be interpreted as commands.

 Bad:
// This is a comment

 Good:
 This is a comment

SC1128: Shebang must be first line

Severity: Warning

Detects shebang on a non-first line.

 Bad:
echo "starting"
!/bin/bash

 Good:
!/bin/bash
echo "starting"

Quoting & Escape Rules

SC1003: Want to escape a single quote?

Severity: Warning

Detects 'don't' patterns where a single quote breaks the string.

 Bad:
echo 'don't do this'

 Good:
echo 'don'\''t do this'
echo "don't do this"

SC1004: Backslash+linefeed in single quotes

Severity: Info

In single quotes, \n is literal backslash-n, not a newline.

SC1012: \t is literal in single quotes

Severity: Info

In single quotes, \t is literal, not a tab. Use $'\t' or double quotes.

 Bad:
echo 'line1\tline2'   # Prints literal \t

 Good:
echo "line1\tline2"   # Prints tab
printf 'line1\tline2'  # printf interprets \t

SC1078: Unclosed double-quoted string

Severity: Error

Detects unmatched double quotes on a line.

SC1110 / SC1111: Unicode quotes

Severity: Error

Detects Unicode curly quotes (\u201c \u201d \u2018 \u2019) that should be ASCII quotes.

 Bad (unicode):
echo \u201chello\u201d

 Good (ASCII):
echo "hello"

SC1098: Quote special characters in eval

Severity: Warning

Detects unquoted variables in eval statements.

 Bad:
eval $cmd

 Good:
eval "$cmd"

Spacing & Formatting Rules

SC1007: Remove spaces around =

Severity: Error

 Bad:
VAR = value

 Good:
VAR=value

SC1068: Don't put spaces around = in assignments

Severity: Error

 Bad:
let x = 1

 Good:
let x=1

SC1069: Missing space before [

Severity: Error

 Bad:
if[ -f file ]; then echo ok; fi

 Good:
if [ -f file ]; then echo ok; fi

SC1101: Trailing spaces after \ continuation

Severity: Warning

Detects invisible trailing whitespace after line continuation backslash.

Syntax Style Rules

SC1065: Don't declare function parameters

Severity: Error

Shell functions don't take named parameters -- use $1, $2, etc.

 Bad:
function myfunc(x, y) {
    echo "$x $y"
}

 Good:
myfunc() {
    echo "$1 $2"
}

SC1066: Don't use $ on left side of assignments

Severity: Error

 Bad:
$VAR=value

 Good:
VAR=value

SC1075: Use elif not else if

Severity: Warning

 Bad:
if [ "$x" = 1 ]; then
    echo "one"
else if [ "$x" = 2 ]; then
    echo "two"
fi
fi

 Good:
if [ "$x" = 1 ]; then
    echo "one"
elif [ "$x" = 2 ]; then
    echo "two"
fi

SC1086: Don't use $ on for loop variable

Severity: Error

 Bad:
for $i in 1 2 3; do echo "$i"; done

 Good:
for i in 1 2 3; do echo "$i"; done

SC1097: Use = not == in [ ]

Severity: Warning

POSIX test uses = for string comparison, not ==.

Here-document Rules

SC1040: With <<-, indent with tabs only

Severity: Warning

The <<- heredoc operator only strips leading tabs, not spaces.

SC1041: Delimiter on same line as <<

Severity: Error

The heredoc body starts on the next line after <<.

SC1044: Unterminated here-document

Severity: Error

The closing delimiter was not found.

SC1120: No comments after heredoc token

Severity: Warning

 Bad:
cat <<EOF # this is a comment
hello
EOF

 Good:
 this is a comment
cat <<EOF
hello
EOF

Unicode & Encoding Rules

SC1017: Literal carriage return

Severity: Error

Detects Windows-style \r\n line endings in shell scripts.

SC1018: Unicode non-breaking space

Severity: Error

Detects invisible \u00a0 characters that look like spaces but aren't.

SC1082: UTF-8 BOM detected

Severity: Warning

Detects the UTF-8 Byte Order Mark (\xef\xbb\xbf) at the start of a file.

SC1100: Unicode dash instead of minus

Severity: Error

Detects en-dash (\u2013) or em-dash (\u2014) used where a minus/hyphen is needed.

SC1109: Unquoted HTML entity

Severity: Warning

Detects &, <, etc. that suggest the script was copy-pasted from a web page.

Bash-in-sh Portability Rules

These rules only fire on #!/bin/sh scripts to catch bashisms.

SC1037: Braces required for positional parameters beyond $9

Severity: Error

 Bad:
echo $10   # Interpreted as $1 followed by literal 0

 Good:
echo ${10}

SC1076: Use $((...)) for math, not $[...]

Severity: Warning

The $[expr] syntax is deprecated. Use $((expr)).

SC1087: Use braces for array access

Severity: Warning

 Bad:
echo $arr[0]

 Good:
echo ${arr[0]}

Source/Include Warnings

SC1090: Can't follow non-constant source

Severity: Info

When source or . is used with a variable argument, static analysis cannot determine which file is sourced.

 Flagged (informational):
source "$config_file"
. "$HOME/.bashrc"

 Not flagged:
source /etc/profile

SC1091: Source file not followed

Severity: Info

The linter notes it is not verifying sourced files.

SC1083: { / } is literal

Severity: Warning

Unquoted braces may be interpreted literally rather than as a group.

Usage

All SC1xxx rules are automatically applied when linting:

 Lint a script (SC1xxx rules included automatically)
bashrs lint script.sh

 Filter output to SC1xxx only
bashrs lint script.sh 2>&1 | grep "SC1"

Shell Type Filtering

Most SC1xxx rules are Universal (apply to all shell types). A few are shell-specific:

• SC1095 (function keyword spacing): NotSh -- only applies to bash/zsh
• SC1037, SC1076, SC1087 (positional params, $[], arrays): ShOnly portability warnings
• SC1105, SC1106, SC1131, SC1139, SC1140: Bash-in-sh portability

bashrs automatically applies the correct rules based on shell type detection.