Basic usage of xargs command

effect

For some commands , Data can only be accepted as command line arguments , And not through stdin Accept the data stream . In this case , There is no way to pipeline data to commands that can only accept command line parameters . The pipeline is only applicable to acceptable stdin As a command of data flow .
xargs The command should immediately follow the pipeline operator , Take standard input as the main source data , Use stdin Execute other commands as command line parameters .

usage

xargs Common command options （ Command line arguments ） Yes ：

-n column :   Specify the number of output columns 
-d flag :  Specify a delimiter for the data source , Split data sources 
-I {
    } :  Place the data source in the specified location after conversion 

When xargs Don't specify -n column Option , that xargs Will stdin coming （ Pipeline symbol implementation ） The source data of is converted into a row , And each parameter is separated by a space , And if you specify -n Option, the source data will be divided into the number of columns corresponding to the following numbers , Similarly, each parameter is separated by spaces . for example ：
1） xargs General use of

# example.txt
1 2 3 4
5 6 7
8 9
#  Convert the data source to 1 That's ok 
cat example.txt | xargs 
1 2 3 4 5 6 7 8 9
#  Convert the data source to 2 Column output 
cat example.txt | xargs -n 2
1 2 
3 4 
5 6
7 8 
9

2） Use of delimiters

#  Use X Split data sources , because xargs After processing, the space is used as the delimiter segmentation result 
echo "splitXsplitXsplitXsplit" | xargs -d X
split split split split

3） Advanced use
1. Read stdin, Pass formatting parameters to the command

#  The test script  ceshi.sh
#!/bin/bash
echo $* '#'

# args.txt
arg1
arg2
arg3

##  Read stdin, Pass formatting parameters to the command 
cat args.txt | xargs -n 2 ./ceshi.sh
arg1 arg2 #
arg3 #

2. Place the data source in a specific location

 for example , You want to provide the data source to the command in the following form ：
./ceshi.sh -p arg1 -a
./ceshi.sh -p arg2 -a
./ceshi.sh -p arg3 -a

That is, you need to specify parameters in -p After the options , At this time, how to use xargs Orders ？
When you need to convert stdin When the source data goes to a specific command line location , have access to xargs Ordered -I Options , stay -I Specify placeholder after option , Then use this placeholder after a specific option , It means that we will start from stdin The converted data will be placed in this location . for example

cat args.txt | xargs -I {
    }  ./ceshi.sh -p {
    } -a
#  The following commands have the same effect as the above commands , But another placeholder is specified ,
cat args.txt | xargs -I []  ./ceshi.sh -p [] -a

4. and find Use it together
   Here are a few simple examples .

# 1. remove the current directory txt Final document 
find . -type f -name "*.txt" | xargs rm -f 

# 2. Count the number of lines of each file in the current directory 
find . -type f -name "*.txt" | xargs wc -l 
#  Equivalent to the following command 
find . -type f -name "*.txt" -exec wc -l {
    } \;