I have the following three constructs in a bash script:
NUMOFLINES=$(wc -l $JAVA_TAGS_FILE) echo $NUMOFLINES" lines" echo $(wc -l $JAVA_TAGS_FILE)" lines" echo "$(wc -l $JAVA_TAGS_FILE) lines"
And they both produce identical output when the script is run:
121711 /home/slash/.java_base.tag lines 121711 /home/slash/.java_base.tag lines 121711 /home/slash/.java_base.tag lines
I.e. the name of the file is also echoed (which I don't want to). Why do these scriplets fail and how should I output a clean:
121711 lines
?
Using “wc -l” There are several ways to count lines in a file. But one of the easiest and widely used way is to use “wc -l”. The wc utility displays the number of lines, words, and bytes contained in each input file, or standard input (if no file is specified) to the standard output. 1.
bash [filename] runs the commands saved in a file. $@ refers to all of a shell script's command-line arguments. $1 , $2 , etc., refer to the first command-line argument, the second command-line argument, etc. Place variables in quotes if the values might have spaces in them.
You can avoid having your filename embedded in the NUMOFLINES variable by using redirection from JAVA_TAGS_FILE, rather than passing the filename as an argument to wc. For example:
NUMOFLINES=$(wc -l < "$JAVA_TAGS_FILE")
The wc utility will not print the name of the file in its output if input is taken from a pipe or redirection operator. Consider these various examples:
# wc shows filename when the file is an argument $ wc -l /etc/passwd 41 /etc/passwd # filename is ignored when piped in on standard input $ cat /etc/passwd | wc -l 41 # unusual redirection, but wc still ignores the filename $ < /etc/passwd wc -l 41 # typical redirection, taking standard input from a file $ wc -l < /etc/passwd 41
As you can see, the only time wc will print the filename is when its passed as an argument, rather than as data on standard input. In some cases, you may want the filename to be printed, so it's useful to understand when it will be displayed.
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