Checking for the correct number of arguments

shell scripting
Andrew K picture Andrew K · Dec 3, 2010 · Viewed 241k times · Source

How do i check for the correct number of arguments (one argument). If somebody tries to invoke the script without passing in the correct number of arguments, and checking to make sure the command line argument actually exists and is a directory.

Answer

Laurence Gonsalves picture Laurence Gonsalves · Dec 3, 2010 
#!/bin/sh
if [ "$#" -ne 1 ] || ! [ -d "$1" ]; then
  echo "Usage: $0 DIRECTORY" >&2
  exit 1
fi

Translation: If number of arguments is not (numerically) equal to 1 or the first argument is not a directory, output usage to stderr and exit with a failure status code.

More friendly error reporting:

#!/bin/sh
if [ "$#" -ne 1 ]; then
  echo "Usage: $0 DIRECTORY" >&2
  exit 1
fi
if ! [ -e "$1" ]; then
  echo "$1 not found" >&2
  exit 1
fi
if ! [ -d "$1" ]; then
  echo "$1 not a directory" >&2
  exit 1
fi

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