在文件的第一列打印大写单词

Question

我想要我的输出：

VDD.
GND
AGNDSUB 
VMEASPOS.
VMEASNEG
VREFEXT 

File1 具有以下信息：

Power and signal 
VDD Digital Power This pin provides power supply connection for the digital
blocks.
GND Digital Ground This pin provides ground connection for the digital blocks.
AGNDSUB Ground This pin provides substrate connection.
VMEASPOS Digital Power Voltage to be measured.
VMEASNEG Ground Ground for the voltage to be measured.
VREFEXT Digital Power Reference voltage input of 1.024V %for VSENS calibration.
operating voltage

Answer 1

与Gnu grep：

grep -Eow '^[[:upper:]]+' file