shell scripting errors

Question

As a part of my homework exercise, i am finding it difficult to execute the following two commands. Can you please rectify the error in it. Thanks in advance

Write a program, that will take a file which has a set of directories, and will look into these directories and their sub directories for any files named core.* and *.o and will print a report of all such files found. (you can use find)

For the above program i attempted to do like this.

cat prog1 | xargs find /$0 -name 'core.*' or '*.o'

But I am getting the following error. (prog1 is a file containing list of directories)

find: paths must precede expression: perl
Usage: find [-H] [-L] [-P] [-Olevel] [-D help|tree|search|stat|rates|opt|exec] [path...] [expression]

The next question is:

Write a script that will go through the /etc/passwd file, and from this print a list of users in the system, their home directory and the shell that they are using

For which I tried the following:

awk '{print "USER \t\t HOME \t\t BASH \n split($0,a,":")}
     {print $a[1] \t\t $a[6] \t\t   $a[7]}' /etc/passwd

I tried googling and seeing the man entries but I don't understand the error. Also can you provide some useful links to shell scripting for beginners?

Slava Semushin · Accepted Answer · 2011-06-19 14:20:09Z

1

Write a program, that will take a file which has a set of directories, and will
look into these directories and their sub directories for any files named core.*
and *.o and will print a report of all such files found.  (you can use find)

I suggest following oneliner:

find `paste -s -d' ' directories.list` -type f -name 'core.*' -or -name '*.o'

Where directories.list contains directories names, one by line.

Write a script that will go through the /etc/passwd file, and from this print a
list of users in the system, their home directory and the shell that they are
using

Try this:

awk -F: 'BEGIN{print "USER\t\tHOME\t\tSHELL"}{printf("%s\t\t%s\t\t%s\n", $1, $6, $7)}' /etc/passwd

answered Jun 19, 2011 at 14:20

Slava Semushin

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4 Comments

CHID Over a year ago

thank you :) it worked.Pls can you tell me what was the error in my approach

Slava Semushin Over a year ago

@chid 1) When xargs invoke find it adds your path to end of command, but find expected it before expressions 2) (as @ignacio-vazquez-abrams already said) find doesn't have or option (use -or or -o instead)

CHID Over a year ago

"adds your path to the end of command" - can you please explain this part?

Slava Semushin Over a year ago

@chid when xargs build command to run it append lines from stdin to command which your specify. In result it executes command like following: find / -name 'core.*' or '*.o' path1 path2 path3 `

Ignacio Vazquez-Abrams · Accepted Answer · 2011-06-19 14:21:35Z

0

Hint 1: find does not understand "or". The operator follows the same pattern as the other options.

Hint 2: awk can use a custom delimiter/field separator.

answered Jun 19, 2011 at 14:21

Ignacio Vazquez-Abrams

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