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Why you should care

Checking arguments is a critical component of Shell script. The $# variable indicates the number of arguments.  If this variable is improperly implemented, then the arguments are left unchecked which can lead to improper execution and bugs in the code.

Business Impacts

Leaving arguments unchecked on multiple shell scripts can be a blow to the overall portfolio.  This can cause productivity issues in an agile-based environment where some developers are trying to debug their code but end up over-complicating the process and leaving other developers without any progress to work towards. [nz_btn text="Production Risk" target="_self" animate="false" animation_type="ghost" color="pink" size="small" shape="rounded" type="normal" hover_normal="opacity" hover_ghost="fill" link="http://casthighlight.wpengine.com/category/product/indicators-methodology/innovation/" icon="icon-office"][nz_btn text="Complexity" target="_self" animate="false" animation_type="ghost" color="mulled_wine" size="small" shape="rounded" type="ghost" hover_normal="fill" hover_ghost="fill" link="http://casthighlight.wpengine.com/category/product/indicators-methodology/innovation/"]

CAST Recommendations

CAST recommends checking arguments by adding spaces between its arguments like the following example below - Incorrect -

if [$# -ne 1]; 
    then echo "illegal number of parameters"
fi

Correct -

if [ "$#" -ne 1 ]; then
    echo "Illegal number of parameters"
fi

Instead of leaving arguments unchecked, they can be removed by adding shift like the following example below -

if (( $# < 3 )); then
  echo "$0 old_string new_string file [file...]"
  exit 0
else
  ostr="$1"; shift
  nstr="$1"; shift  
fi

These errors usually occur because the style-guide in the company is not followed by development teams or has not been updated for future projects.  For more help on checking arguments, refer to "Scripting Guide for Bash"

References

https://stackoverflow.com/questions/18568706/check-number-of-arguments-passed-to-a-bash-script?rq=1 https://unix.stackexchange.com/questions/174566/what-is-the-purpose-of-using-shift-in-shell-scripts[nz_btn text="Shell Script Guide" target="_self" animate="false" animation_type="ghost" color="turquoise" size="small" shape="rounded" type="ghost" hover_normal="fill" hover_ghost="fill" link="http://tldp.org/LDP/abs/html/" icon="icon-book"]

How we detect

This code insight counts one violation each time the following patterns are encountered :

• <indentifier> = $#
• $#  <op> where <op> is  -eq, -ne, -lt, -gt, -le, -ge, =, !=
• case $#

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