CODEWITHSUNDEEP
bashshell
GJain
GJain

Reputation: 5093

how to pipe wc -l output to echo output

I count errors in a log file by doing grep error logfile | wc -l

It outputs 10

I want to print Error count found in logfile is 10

I think need to pipe it thru echo but how can I append 10 to echo output?

I tried

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

Upvotes: 8

Views: 16578

Answers (6)

zmo
zmo

Reputation: 24812

you should not pipe the var into echo, but instead run them in sequence:

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

or you can define the variable just for the echo command, by doing with bash:

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

As said in the comments below, of course you can embed your command call in your echo statement:

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

Upvotes: 9

0PT1MU5 PR1ME
0PT1MU5 PR1ME

Reputation: 45

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

Upvotes: -1

Jeffrey Cash
Jeffrey Cash

Reputation: 1073

Here are some more examples of different ways to handle this task, just to help you get a feel for bash's features and options:

(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"

If you want to go out of your way to use a "here string":

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

Also, here's a bash builtin only option:

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

Upvotes: 1

Inian
Inian

Reputation: 85780

Use printf and grep with -c flag for pattern count.

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

The flags used in GNU grep

-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.

Upvotes: 2

mklement0
mklement0

Reputation: 439193

To simply embed the (stdout) output from a command in a string, without the need to also store that output in a variable, simply use a command substitution ($(...)) inside a double-quoted string ("..."):

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

As pointed out in Inian's answer, grep supports counting matches directly, via its -c option, so the above can be simplified to:

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

Using a variable to store grep's output is only needed if you need to refer to it again later:

var=$(grep -c error logfile)
echo "Error count found in logfile is $var"
# ... use $var again as needed

As for what you've tried: echo only accepts command-line arguments, not stdin input, so using a pipeline (... | echo ...) is the wrong approach.

Upvotes: 4

chris01
chris01

Reputation: 12377

Use apostrophes.

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

Upvotes: -1

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