Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: Code explanation?
Top Forums UNIX for Dummies Questions & Answers Code explanation? Post 302583532 by ryran on Tuesday 20th of December 2011 03:34:52 PM
Old 12-20-2011
Quote:
Originally Posted by kotsos13
As i said before he didn't taught us the cut command and now i have to learn the code without cut Smilie
In this command how do i understand pulling out only the username and the uid?
I'm sorry man. I love sed, and I use it for all kinds of things, but I would never use it for this. ... I don't understand how it's being used here, and I don't quite care to try and muddle through it and figure it out, though I'd be curious to have someone explain it. If your uh... unorthodox.. instructor won't explain it to you (and no one else answers), you could try to puzzle through it with the help of the sed info page (type info sed).

As a consolation prize, here's a command that does the same thing your instructor's original command was supposed to do, but more simply and more efficient. Maybe he'll be impressed. Smilie
HTML Code:
awk -F: '/^[^:][^:][^:][^:]:/ {print $1" "$3}' /etc/passwd | sort -t' ' -k2 -nr
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Need explanation for the syntax(code)

Hi I am new to shell script programming... want to know the process of the following: if then echo "$0: missing argument for option(s) :$MISSINGOPTARG" echo "usage" $USAGE" exit 1 fi (1 Reply)
Discussion started by: chandhar
1 Replies

2. Shell Programming and Scripting

tr explanation please

how does below tr command replace nonletters with newlines? I think I understand tr -cs '\n' part.. but what is A-Za-z\' <--- what is this?? tr -cs A-Za-z\' '\n' | -c --complement -s, --squeeze-repeats replace each input sequence of a repeated character that is... (0 Replies)
Discussion started by: convenientstore
0 Replies

3. Shell Programming and Scripting

AWK deifnition and some small code explanation

Could someone give me a quick simple explanation for the AWK command. And also help me to explain the code i have made. I have made some general comments about it myself. I was wondering if people could help me with the rest: awk -F'' 'END { fmt = "%-20s\t%s\t%s\n" ... (0 Replies)
Discussion started by: amatuer_lee_3
0 Replies

4. Shell Programming and Scripting

nawk code explanation

Hi I have a line/command which greps certain pattern () from the file and 22 lines AFTER that: nawk '/\/{c=22}c&&c--' input_file Can somebody explain the coding in this command (what " c&&c-- " does)? and how to modify this command to output 22 lines BEFORE this pattern () Thanks a lot ... (3 Replies)
Discussion started by: aoussenko
3 Replies

5. Homework & Coursework Questions

Please help with the following fork code..with complete explanation

I have the following piece of codes. Please explain it to me in great detail how are these codes working. 1. #include <stdio.h> int main(){ int x; x=0; while (x<2 && fork()){ if (!fork()) execlp("echo","x++","x",0); x++; system("echo x+x"); } } 2. #include <stdio.h> int i;... (1 Reply)
Discussion started by: prakashabii
1 Replies

6. UNIX for Dummies Questions & Answers

In need of explanation

Its great someone provided this script that strips out a filename and extension but can someone explain how each line works? file1='Jane Mid Doe.txt' newfile='Jane.txt' 1) ext=${file1##*.} 2) filename=${file%%.???} 3) set -- $filename 4) newfile="1.$extension" (1 Reply)
Discussion started by: Lillyt
1 Replies

7. Shell Programming and Scripting

code explanation

Can you please explain the following code plz? my_cd=' ' while getopts :e: OPTION; do case "$OPTION" in e) my_cd ="$OPTARG";; esac done if ; then echo " >>> ERROR - I am wrong" echo " >>> ERROR - Hello" exit 99 fi What I don't understand is what is OPTION or... (3 Replies)
Discussion started by: RubinPat
3 Replies

8. UNIX for Dummies Questions & Answers

Explanation of NAWK Code

Hi all, I need your help in understanding the meaning and syntax of the below nawk line. Here is an extract of a script which I use daily and works well. The script extracts the hostnames and messages within a syslog file. I would also like to extract the message time in the 3rd column by... (2 Replies)
Discussion started by: wthomas
2 Replies

9. Homework & Coursework Questions

Minix 3 Source Code Organisation Explanation

1. I've been asked to provide a detailed description on how Minix's source code is organised. This may sound slightly simple, but what exactly am I to refer to when explaining? Any documents that would provide assistance to understand whats being asked? Thanks 2. Not applicable: 3.... (1 Reply)
Discussion started by: Menace12
1 Replies

10. Shell Programming and Scripting

ksh code explanation

Hi. Can somebody please explain the following lines of KSH code for me? The code checks all sub directories in a specific location which are numbered (E.g. test_01, test_02 ... etc.), then finds the one with highest number and extracts that number from the dir name into the variable num. I'd just... (9 Replies)
Discussion started by: user052009
9 Replies

LEARN ABOUT LINUX

shtool-subst

SHTOOL-SUBST.TMP(1)					      GNU Portable Shell Tool					       SHTOOL-SUBST.TMP(1)

NAME

       shtool-subst - GNU shtool sed(1) substitution operations

SYNOPSIS

       shtool subst [-v|--verbose] [-t|--trace] [-n|--nop] [-w|--warning] [-q|--quiet] [-s|--stealth] [-i|--interactive] [-b|--backup ext]
       [-e|--exec cmd] [-f|--file cmd-file] [file] [file ...]

DESCRIPTION

       This command applies one or more sed(1) substitution operations to stdin or any number of files.

OPTIONS

       The following command line options are available.

       -v, --verbose
	   Display some processing information.

       -t, --trace
	   Enable the output of the essential shell commands which are executed.

       -n, --nop
	   No operation mode. Actual execution of the essential shell commands which would be executed is suppressed.

       -w, --warning
	   Show warning on substitution operation resulting in no content change on every file. The default is to show a warning on substitution
	   operations resulted in no content change on all files.

       -q, --quiet
	   Suppress warning on substitution operation resulting in no content change.

       -s, --stealth
	   Stealth operation. Preserve timestamp on file.

       -i, --interactive
	   Enter interactive mode where the user has to approve each operation.

       -b, --backup ext
	   Preserve backup of original file using file name extension ext.  Default is to overwrite the original file.

       -e, --exec cmd
	   Specify sed(1) command directly.

       -f, --file cmd-file
	   Read sed(1) command from file.

EXAMPLE

	#   shell script
	shtool subst -i -e 's;(c) ([0-9]*)-2000;(c) 1-2001;' *.[ch]

	#    RPM spec-file
	%install
	    shtool subst -v -n 
		-e 's;^(prefix=).*;1 $RPM_BUILD_ROOT%{_prefix};g' 
		-e 's;^(sysconfdir=).*;1 $RPM_BUILD_ROOT%{_prefix}/etc;g' 
		`find . -name Makefile -print`
	    make install

HISTORY

       The GNU shtool subst command was originally written by Ralf S.  Engelschall <rse@engelschall.com> in 2001 for GNU shtool.  It was prompted
       by the need to have a uniform and convenient patching frontend to sed(1) operations in the OpenPKG package specifications.

SEE ALSO

       shtool(1), sed(1).

18-Jul-2008							   shtool 2.0.8 					       SHTOOL-SUBST.TMP(1)
All times are GMT -4. The time now is 09:11 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy