Entering directory through unix bash script issue

Question

Be aware that this code i'm about to post is purposefully not perfect and will not work should there be a a text file in the directory but the full code does have such a check. But the issue is that this:

#!/bin/bash 
for d in *; do 
    cd $d 
done

produces:

./test: line 3: cd: 500: No such file or directory 
./test: line 3: cd: 536: No such file or directory 
./test: line 3: cd: 560: No such file or directory 
./test: line 3: cd: 572: No such file or directory 
./test: line 3: cd: out.txt: No such file or directory 
./test: line 3: cd: prob1: No such file or directory 
./test: line 3: cd: problem2: No such file or directory 
./test: line 3: cd: README: No such file or directory 
./test: line 3: cd: test: No such file or directory

where 500, 536, 560, and 572 are directories that should be able to be opened. If I do just a cd 500 then I can go into the directory without an issue. But it will not work when I use the automated process in the shell script.

alright so after further going into the program i now have:


#!/bin/bash
cd "$1"
for d in */; do
    (
         cd "$d"
        for file in $*; do
        (
                bla="$(head -4 $file|tail -1)"
                cd ~cfb43/cs265/a1
                echo $bla > out.txt
                cd
                cd "$1"
                cd "$d"
        )
        done
        cd "$1"
    )
done

and i receive:


head: error reading `/home/cfb43/cs265/a1': Is a directory
head: error reading `/home/cfb43/cs265/a1': Is a directory
head: error reading `/home/cfb43/cs265/a1': Is a directory
head: error reading `/home/cfb43/cs265/a1': Is a directory
head: error reading `/home/cfb43/cs265/a1': Is a directory

All i want to do is go into a directory and read from a file and get the fourth line of text and print it to out.txt in my folder. I'm not sure why this code is getting stuck at a1 and not atleast 500 or something like that. any further help and i would be very greatful

user000001 · Accepted Answer · 2013-10-12 16:25:02Z

5

Because you try to enter the next subdirectory without leaving the previous one. You could do

#!/bin/bash 
for d in */; do 
    cd -- "$d"
    # do some stuff
    cd .. 
done

or use a subshell

#!/bin/bash 
for d in */; do 
    (
        cd -- "$d"
        # do some stuff
    )
done

answered Oct 12, 2013 at 16:25

user000001

33.7k14 gold badges86 silver badges113 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Colan Biemer Over a year ago

could you possibly look at the new portion of the question because what you said worked but led to new issues. also why do you have the "--" in the cd command?

user000001 Over a year ago

@ColanBiemer The -- is for guaranteeing that if a directory name starts with - (e.g. -mydir) it will not be interpreted as an option to the cd command, but as a directory name. Regarding your new error message, it looks like you call head on a directory. You should check that the operant is a regular file with if [[ -f "$file" ]].

Nahuel Fouilleul · Accepted Answer · 2013-10-12 19:59:52Z

1

are you sure of what you are doing: $* which expands to parameters $1 $2 .. ${!#}

for file in $*; do

maybe you want: * which expands to files in current directory

for file in *; do

Another way to do is to never change directory:

for file in */*;do
   head -4 "$file" | tail -1 >> ~cfb43/cs265/a1/out.txt
done

and another way to do

head -4 | tail -1

with sed

sed n '4{p;q}'

with awk

awk 'NR==4{print;exit}'

with perl

perl -ne 'if($.==4){print;exit}'

edited Oct 12, 2013 at 19:59

answered Oct 12, 2013 at 19:36

Nahuel Fouilleul

19.5k2 gold badges36 silver badges37 bronze badges

1 Comment

Colan Biemer Over a year ago

when i did that i got head: cannot open `*' for reading: No such file or directory where i then had to exit out of it

Collectives™ on Stack Overflow

Entering directory through unix bash script issue

2 Answers 2

2 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related