Under the folder /usr/hdp/ We have .jar files as the following

$ ls  /usr/hdp/ | grep ".jar"

I want to count all characters from the .jar files by wc , in order to understand if .jar files renamed

So I do the following command in order to count all characters from all .jar files

ls  /usr/hdp/ | grep ".jar" | sed s'/\// /g' | awk '{print $NF}' | wc | awk '{print $NF}'

So in this case we get 758 characters from all .jars

But the command isn’t elegant

How we can improve the command to be better?

  • 1
    You want to get total string length of all the filename? That sounds like a strange request. Smells like an XY problem. – glenn jackman Feb 28 '19 at 19:08
  • what I want it to count all characters from the output by wc or any other suggestion – yael Feb 28 '19 at 19:17
  • 1) Wouldn't it make sense to get the length of "each" filename? 2) That wouldn't really tell you a whole lot as it can be renamed to something with the same amount of letters. 3) There really isn't a way to tell if any of the files have been renamed unless a script runs something like ls -l | awk '{print $NF} > jarlog.txt so that you can compare the filenames. – Nasir Riley Feb 28 '19 at 19:22
  • look only I want is to improve the cli - ls /usr/hdp/ | grep ".jar" | sed s'/\// /g' | awk '{print $NF}' | wc | awk '{print $NF}' – yael Feb 28 '19 at 19:24
  • 1
    printf '%s\n' *.jar | md5sum wouldn't be blind to renaming to something with the same amount of letters. – Kamil Maciorowski Feb 28 '19 at 19:32

Most probably you are looking for

basename -a /usr/hdp/*.jar | wc -c

The path with wildcard list all jar files, the basename command strips directories (-a is needed to accept many arguments), and wc -c just counts bytes (if some filenames consist of 2 byte characters then perhaps wc -m (characters count) would be a better choice).

However, to if the goal is to check if files have been modified then perhaps stat (for modification time) or md5sum/shasum for checksum would be a better tools.

  • 1
    wc -c counts the number of bytes, not characters. wc -m counts the number of characters. Also note that you're also counting one extra newline character per file. – Stéphane Chazelas Feb 28 '19 at 19:47
  • what is the diff between wc -c to wc -m ? ( because on both I get the same results ) – yael Feb 28 '19 at 19:51
  • 2
    @yael, wc -m counts the number of characters, wc -c the number of bytes. That makes a difference in the case of characters made of more than one byte (in UTF-8, that's all the non-ASCII ones (over a million of them)). Compare printf € | wc -c with printf € | wc -m. – Stéphane Chazelas Feb 28 '19 at 19:53

Counting the number of letters in the filenames would not be a safe way of detecting a renamed filename.

Instead, create a simple file listing of the names, and compare it to an existing list. By using diff, you would be shown exactly which line(s) in the list had changed.




echo /usr/hdp/*.jar >"$newlist"

if [ -f "$oldlist" ]; then
    diff -u "$oldlist" "$newlist"

mv "$newlist" "$oldlist"

Obviously, the first time you do this, filelist.old would not exist, so the diff would not run.

Note that I save the full path to each file in the output file. This does not matter since the directory path is static.

Change echo to ls -l if you want to also compare timestamps etc. Change it to stat if you want to compare even more meta data (this would generate diff output when even the last-access timestamp on a file changed). Install wdiff and change diff to wdiff to get a word-based diff rather than a line-based one.

The LC_ALL=C is to guarantee a consistent sorting of the expansion of the shell glob.


To just get the number of characters in the (non-hidden) jar filenames, I would do

cd /usr/hdp/ && printf %s *.jar | wc -m

This will not count any newlines, just the filename characters (replace wc -m with wc -c for the number of bytes instead of characters).

Purposefully, I'm not parsing ls output.

  • Note that in shells like bash, if there's no .jar file in the current directory, that will output 5 (the number of characters in *.jar). In bash, you can do shopt -s nullglob to get 0 in that case. – Stéphane Chazelas Feb 28 '19 at 19:51

I don't understand the point of the sed command, you are replacing a slash with a space? Why?

Aside from that, it seems that you want to count the total number of characters in all the file names of the .jar files. IF so, try this:
ls /usr/hdp/*.jar | sed s'/// /g' | wc -c

Two other possibilities for your sed command:
sed "s|/| |g" -- or -- tr '/' ' '
Since your ls command won't show directory names, I am not sure you need it.
This will also count the LF at the end of each file name. Is that OK?

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