当使用cat找不到参数时Bash打印帮助消息

Question

帮助消息

Usage: concat FILE ...
Description: concatenates FILE(s) to standard output separating them with divider -----.

代码

#!/bin/bash
# concat script
if [[ $@ ]]
then
        for i in "$@"
        do
         cat "$i" && echo  "-----"
        done
exit 0
else
 cat 2> "Usage: concat FILE ...
Description: concatenates FILE(s) to standard output separating them with divider -----."
exit 1
fi

Answer 1

cat用于从文件输出数据。若要从字符串输出数据，请使用echo。

2>用于将stdout重定向到文件。若要将stdout指向stderr，请使用>&2。

总而言之：

echo >&2 "Usage: concat FILE ...
Description: concatenates FILE(s) to standard output separating them with divider -----."

cat << EOF >&2
Usage: concat FILE ...
Description: concatenates FILE(s) to standard output separating them with divider -----.
EOF