如何抑制grep的输出? [英] How can I suppress output of grep?

问题描述

当我运行此命令时，当grep成功执行时，它还会在文件中打印实际的$item.我不想打印内容/$item.我只想显示我的回声.

When I run this command, it also prints the actual $item in the file when the grep is successful. I do not want to print the content/$item. I just want to show my echo.

我该怎么办?

if grep $item filename; then
   echo it exist
else
    echo does not exist
fi

推荐答案

使用-q:

if grep -q "$item" filename; then
   echo "it exists"
else
    echo "does not exist"
fi

或在一个班轮中:

grep -q "$item" filename && echo "it exists" || echo "does not exist"

---

来自man grep

-q ，--quiet，--silent

-q, --quiet, --silent

安静； 请勿在标准输出中写入任何内容.立即退出 如果找到任何匹配项，则状态为零，即使检测到错误也是如此. 另请参见-s或--no-messages选项. (-q由POSIX指定.)

Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. (-q is specified by POSIX.)

---

如下面的AdrianFrühwirth点，grep -q只会使STDIN静音.如果要摆脱STDERR，可以将其重定向到/dev/null:

---

As Adrian Frühwirth points below, grep -q alone will just silence the STDIN. If you want to get rid of the STDERR, you can redirect it to /dev/null:

grep -q foo file 2>/dev/null

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