diff --git a/README.md b/README.md index d91f962..6f3e4a9 100644 --- a/README.md +++ b/README.md @@ -358,6 +358,7 @@ 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 +unset var[i] # Array index treated as glob ``` ### Conditionals @@ -376,6 +377,7 @@ ShellCheck can recognize many types of incorrect test statements. [ grep -q foo file ] # Command without $(..) [[ "$$file" == *.jpg ]] # Comparisons that can't succeed (( 1 -lt 2 )) # Using test operators in ((..)) +[ x ] & [ y ] | [ z ] # Accidental backgrounding and piping ``` ### Frequently misused commands @@ -447,6 +449,8 @@ echo "Hello $name" # Unassigned lowercase variables cmd | read bar; echo $bar # Assignments in subshells cat foo | cp bar # Piping to commands that don't read printf '%s: %s\n' foo # Mismatches in printf argument count +eval "${array[@]}" # Lost word boundaries in array eval +for i in "${x[@]}"; do ${x[$i]} # Using array value as key ``` ### Robustness @@ -471,6 +475,7 @@ ShellCheck will warn when using features not supported by the shebang. For examp 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 +expr match str regex # Unportable alias for `expr str : regex` trap 'exit 42' sigint # Unportable signal spec cmd &> file # Unportable redirection operator read foo < /dev/tcp/host/22 # Unportable intercepted files @@ -491,10 +496,15 @@ 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 +!# bin/bash -x -e # Common shebang errors echo $((n/180*100)) # Unnecessary loss of precision ls *[:digit:].txt # Bad character class globs sed 's/foo/bar/' file > file # Redirecting to input +var2=$var2 # Variable assigned to itself +[ x$var = xval ] # Antiquated x-comparisons +ls() { ls -l "$@"; } # Infinitely recursive wrapper +alias ls='ls -l'; ls foo # Alias used before it takes effect +for x; do for x; do # Nested loop uses same variable while getopts "a" f; do case $f in "b") # Unhandled getopts flags ```