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Detector Library

Shell detectors (173/173)

Ineffective Variable Assignment End token not found Invalid ShellCheck Directive Placement Variable Assignment Syntax SSH Stdin Interference Glob Pattern Safety Sensitive bourne shells Avoid LS-Grep Unrecognized shebang Shebang Mismatch String Length Calculation Unicode Dash In Command Ensure no spaces are used Grouping expressions Single quotes strictly terminate Unnecessary Single Quotes Leading Zero Arithmetic Backslash followed by a linefeed Use of terminate commands Missing exec Terminator Incorrect Tick Usage Semicolons directly after else Array Element Separation Apostrophe terminated single quoted string Invalid Unary Test Operator Sudo Redirect Misuse Shebang Placement Incorrectly used escape sequences Improper use of curly braces Missing Space Before Colon Printf Variable Interpolation Pipeline Assignment Syntax Non Portable Character Class Here-Document Command Terminator Placement Test operator missing an operand Expr Modernization Missing Function Opening Brace Missing Space Before Comment Arithmetic Expression Syntax Reversed Shebang Command Substitution Execution Unsupported Decimal Comparison Semicolons directly after then ShellCheck Directive Placement Missing Space After Function Name Unquoted Regex Matching Missing Space Before Negation Redirection Misinterpretation Unexpected Directive Unquoted Special Parameters Command Expansion Error Do not use unicode non-breaking space Unnecessary Brackets In Tr Unquoted Command Substitution Incorrect Redirection Order Unexpected opening parenthesis Incorrect Regex Operator Unicode Quote Usage Single-Iteration Loop Integer Division Precision Loss File Read-Write Race Condition Unable To Follow Source Invalid Parentheses Usage Trailing Space After Backslash Shebang Syntax Correction Unquoted tr Arguments Use shell logical operators Incorrect Command Substitution in Find Exec Non-empty then clause Incorrect Comment Syntax Suspicious End Quote Directive Comment Syntax Unmatched Keyword Unbraced Array Expansion Prefer Find Over LS Missing Do Keyword Then after if statement Invalid Test Operator Usage Unquoted Ampersand in Command Null-Terminated Filename Handling Function in External Command Avoid Complex Logical Expressions Unquoted RHS Comparison Incorrect Keyword Capitalization Unquoted Array Expansion Test Bracket Termination Unnecessary Exec Command Document is not properly terminated Constant Comparison Sensitive whitespace of bourne shells Avoid escaping parentheses Tr Misused For Word Replacement Incorrect Logical Operator Bracket Spacing in Conditional Statements Command Assignment Incorrect Numeric Comparison Unquoted Eval Argument Here-doc Whitespace Useless Cat Elimination UTF-8 BOM Present Glob-based Iteration PS Grep Alternative Glob Matching in Test Brackets Unnecessary Dollar In For Loop Here-Document End Token Isolation Dollar should be escaped with a backslash Unnecessary Quoting in Loop Here-doc Comment Only literals can be escaped Unquoted Grep Patterns Find Print Zero Usage Misused Regex Operator Incorrect Branching Keyword Invalid unary test operator usage Detects if statement without terminator Unquoted Find Patterns Unexpected Redirection in Comparison Shells are space sensitive Process only removes tabs Missing Spaces in Comparison Misplaced Line Continuation Operator POSIX Shell Compatibility Arithmetic Expansion Command Execution Shell Prompt Escape Sequences Echo Escape Sequences Command Argument Handling Brace Expansion Limitation Escape Dollar Sign in Quotes Parsing Error Braces required for positionals Unnecessary Backslash Escape Non Constant Source Variable Indirection Tilde Expansion Unnecessary Variable Expansion Use of if and then Incorrect Equality Operator Unescaped Variable in Remote Command Unnecessary Echo Pipe Keywords being used as arguments Unescaped Variable Find Loop Safety Read Lines with While Loop Unclosed String Unclosed Do Statement Misplaced ShellCheck Directive Regex Asterisk Misuse Source Parsing Failed Backtick Command Injection Unnecessary Echo Unintended Literal Brace Incorrect Function Parameter Declaration Multi-Parameter Shebang Subshell Variable Modification Shell Alias Nesting Here-Doc Termination Linefeed Incorrect Grep Pattern Remove indentation before end token Syntax Error Detection Incorrect Conditional Syntax Remove Leading Spaces Before Shebang Unsupported Script Language Incorrect Quoting in Trap Commands Missing Dollar Sign Missing Shebang Premature Variable Expansion Unquoted Variable in Test Here Document Expansion Control Arithmetic Expansion Modernization Dollar Sign In Assignment Unused Variable Detection Command Substitution Syntax Parameter Expansion for String Manipulation

Useless Cat Elimination Low

Using 'cat' to read a single file and pipe its contents to another command is inefficient and unnecessary. Instead, use input redirection ('<') or provide the filename directly to commands that accept file arguments.

Detector ID

shell/useless-cat-elimination@v1.0

Category

Common Weakness Enumeration (CWE)

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Tags

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Noncompliant example

1
2# Noncompliant: Unnecessary use of `cat` to pipe file contents to grep.
3cat log.txt | grep "error"

Compliant example

1
2# Compliant: Directly using grep with file as argument, avoiding unnecessary `cat`.
3grep "error" log.txt