Question

我通过grep error logfile | wc -l

计算日志文件中的错误

输出10

我想打印Error count found in logfile is 10

我认为需要通过回声来管道它，但我怎样才能将10附加到回声输出？

我试过

 var="$(grep -i error logfile | wc -l)" | echo "Error count found in logfile is $var"

Answer 1

使用printf和grep -c标志进行模式计数。

printf "Error count found in logfile is %s\n" "$(grep -chi error logfile)"

GNU grep

中使用的标志

-c, --count
       Suppress normal output; instead print a count of matching lines for each input file.  
       With the -v, --invert-match option  (see  below),  count  non-matching lines.

-h, --no-filename
       Suppress the prefixing of file names on output.  This is the default when there is 
       only one file (or only standard input) to search.

-i, --ignore-case
          Ignore case distinctions in both the PATTERN and the input files.

Answer 2

你不应该将var传递给echo，而是按顺序运行它们：

var="$(grep -i error * | wc -l)"
echo "Error count found in logfile is $var"

或者你可以通过 bash 来为echo命令定义变量：

 var="$(grep -i error * | wc -l)" ; echo "Error count found in logfile is $var"

如下面的评论中所述，您当然可以在echo语句中嵌入命令调用：

echo "Error count found in logfile is $(grep -i error * | wc -l)"

Answer 3

要简单地将命令中的（stdout）输出嵌入到字符串中，而不需要将该输出存储在变量中，只需使用命令替换（{{1} }）在双引号字符串（$(...)）：

中

"..."

正如Inian's answer所指出的，echo "Error count found in logfile is $(grep error logfile | wc -l)"支持通过其grep选项直接计算匹配，因此上述内容可以简化为：

-c

只有在以后需要再次参考时，才需要使用变量来存储echo "Error count found in logfile is $(grep -c error logfile)"的输出：

grep

至于您尝试过的内容：var=$(grep -c error logfile) echo "Error count found in logfile is $var" # ... use $var again as needed只接受命令行参数，而不接受stdin输入，因此使用管道（echo）是错误的方法

Answer 4

以下是处理此任务的不同方法的更多示例，只是为了帮助您了解bash的功能和选项：

(echo -en "Error count found in logfile is "; grep error logfile | wc -l)

{ printf "Error count found in logfile is " && wc -l < <(grep error logfile); }

printf 'Error count found in logfile is %d\n' $(grep -c error logfile)

awk '/error/{++c} END{printf "Error count found in logfile is %d\n", c}' logfile

var=$(grep -c error logfile); echo "Error count found in logfile is $var"

如果您想要使用“here string”：

cat<<<"Error count found in logfile is $(grep -c error logfile)"

此外，这里只有一个bash内置选项：

declare -i c=0
while read l; do
  [[ $l == *error* ]] && ((++c))
done < logfile
echo "Error count found in logfile is $c"`

Answer 5

使用撇号。

var=`cat x.dat | grep error | wc -l`
echo $var

Answer 6

echo "Error count found in logfile is "$(grep error logfile | wc -l)

如何将wc -l输出传递给echo输出

6 个答案: