判断

判断目录是否存在

if [ -d "$dir" ]; then
  echo "directory $dir exists"
else
  echo "directory $dir does not exist"
fi

判断文件是否存在

if [ -f "$file" ]; then
 echo "file $file exists"
else
 echo "file $file does not exist"
fi

判断命令是否存在

if ! command -v jq &>/dev/null; then
  echo "jq not installed"
  exit 1
fi

判断命令是否执行成功

if mount bpffs /sys/fs/bpf -t bpf 2>/dev/null; then
  echo "mount bpffs success"
fi

判断上个命令是否执行成功

if [ $? -eq 0 ]; then
  echo "last command executed successfully"
else
  echo "last command executed failed with status code $?"
fi

if [ $? -ne 0 ]; then
  echo "last command executed failed with status code $?"
else
  echo "last command executed successfully"
fi