Bash-scripting, usage of the 'for' loop

Question

I am trying to write a simple bash script that displays the contents of files.

#!/bin/bash

echo 'Input the path of a file or directory...'
read File

if [ -e $File ] && [ -f $File ] && [ -r $File ]
    then
    echo 'Displaying the contents of the file '$File
    cat $File


elif [ -d $File ] && [ -r $File ]
then
echo 'Displaying the contents of the directory '$File       
    for FILE in `ls -R $File`
        do
               cd $File/$FILE
               echo 'Displaying the contents of the file '$FILE
               cat $FILE
        done

else 
echo 'Oops... Cannot read file or directory !'
fi

The user should input a file or directory path. If the user inputs a file the program displays it with cat. If the user inputs a directory it should display the content of all files including those in the subdirectories. That part of the program doesn't work very well. I would like to get a result that doens't display errors like 'No such file or directory' but only the content of files. Can you help me ? Thanks in advance.

Never use `for i in $(command)` . See this answer for more details : http://stackoverflow.com/questions/19606864/ffmpeg-in-a-bash-pipe/19607361#19607361 Otherwise, I think that the best solution is to use `find` as described in some answer of this thread. — Idriss Neumann, Oct 28 '13 at 21:20

evil otto · Accepted Answer · 2013-10-30T22:53:14.450

6

ls -R is the wrong tool to find all files in all subdirectories. find is a much better choice:

echo "displaying all files under $File"
find "$File" -type f -printf "Displaying contents of %p\n" -exec cat {} \;

edited Oct 30 '13 at 22:53

answered Oct 28 '13 at 16:41

evil otto

10,348
25
38

Thanks for your response ! The code works fine, but is there a way to print the name of the file just before displaying its content ? – buster Oct 28 '13 at 17:18
`… -exec echo {}; cat {} \;` – chepner Oct 28 '13 at 17:23
Thanks chepner, but I get '' find: missing argument to `-exec' ''. – buster Oct 28 '13 at 17:33
1

... -exec echo "Filename: {}" \; -exec cat {} \; --- edited answer – evil otto Oct 28 '13 at 20:31
1

Don't use `-exec echo ...` it's silly. Use `-printf "Displaying contents of %p\n"` (or `%f`) instead. – gniourf_gniourf Oct 28 '13 at 22:37

score 3 · Answer 2 · answered Oct 28 '13 at 16:41

3

You can print all files in the current directory just doing

for f in * do
    cat $f;
done

answered Oct 28 '13 at 16:41

LeartS

2,866
2
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45

Yes but in the for loop he can add other commands (like the "debug" echo he has) easily. I just gave him the structure. Why wrong? – LeartS Oct 28 '13 at 16:47
You are correct the loop allows more flexibility. The main issue is a `for` loop is the wrong approach. The OP uses `ls -R` which clearly means subdirectories are expected. Neither his loop nor yours handle this case properly. `find`is the way to go. – jlliagre Oct 28 '13 at 16:55
You can do recursive with `shopt -s nullglob globstar; for subdir in **/*/` but then it gets tedious to separate out file and directories. `find` is certainly easier if you just want to cat files. – glenn jackman Oct 28 '13 at 17:30

SilverCode · Answer 3 · 2013-10-28T22:25:44.447

2

the find command will save you a lot of the logic:

#!/bin/bash 

echo 'Input the path of a file or directory...'
read File
DirName="."

if  echo $File | grep '/' ;  then
  DirName=$(dirname $File)
  File=$(basename $File)
fi

find "$DirName" -type f -name "$File" -exec cat {} \;
find "$DirName" -type d -name "$File" -exec ls {}

The first find will look for all 'regular' (-type f) files name $File and cat them The second find will look for all 'directories' (-type d) and list them.

If they do not find any then the -exec portion will not execute. The grep will split the path is there is a slash in there.

edited Oct 28 '13 at 22:25

answered Oct 28 '13 at 16:43

SilverCode

189
4

Thanks for your response ! When I try to run your script I get an error ''find: warning: Unix filenames usually don't contain slashes...''. – buster Oct 28 '13 at 17:23
to get around that you can split the name using basename and dirname e.g. find $(dirname $File) -name "$(basename $File)" – SilverCode Oct 28 '13 at 21:58

Bash-scripting, usage of the 'for' loop

3 Answers3