Need explanation of script

Thread Tools Search this Thread
Top Forums Shell Programming and Scripting Need explanation of script
# 1  
Old 11-25-2007
Need explanation of script


Can anybody explain what this script is doing?

who | cut -d " " -f1 | sort -u > userlist1
while true ; do
sleep 60
who | cut -d" " -f1 | sort -u >userlist2
for username in `cat userlist1` ; do
if ! grep "^$username$" userlist2 > /dev/null ; then
echo "$username has logged out"
for username in `cat userlist2` ; do
if ! grep "^$username$" userlist1>/dev/null; then
echo "$username hass logged in"
mv userlist2 userlist1;

Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Shell script explanation

Hey, can someone explain me this script? i=0 while read WORT do echo $WORT|grep a>/dev/null || echo$WORT|grep B>dev/null || let i=$i+1 done echo $i The first lane initializie the variable i with the value of 0. The loop line has 3 different options because of ||. The only option I... (10 Replies)
Discussion started by: newuser21
10 Replies

2. Shell Programming and Scripting

What does this shell script do? Need in depth explanation please

Hi My friend wrote this particular script and won't tell me what it does, and when I run it I don't understand it. What does the entire script do with specifics please. Thanks Bob #!/bin/bash current=0 while ; do if ; then echo ${current} current=$((${current}+1)) fi done (1 Reply)
Discussion started by: shadowknight777
1 Replies

3. Shell Programming and Scripting

Explanation of FNR in this awk script

To merge mutiple *.tab files as: rs1 A A rs2 A A rs3 C C rs4 C Cfile2.ind rs1 T T rs2 T T rs3 G G rs4 G Gand rs1 B B rs2 B B rs3 L L rs4 L LOutput: AA TT BB AA TT BB CC GG LL CC GG ... (4 Replies)
Discussion started by: yifangt
4 Replies

4. Solaris

Explanation of script

Hello Guys, can someone help explain the script below for me? I will really appreciate it. vi db_script #!/bin/sh echo .cron job run on.`date`> cronjob.txt df -h >> cronjob.txt echo welcome to home (2 Replies)
Discussion started by: cjashu
2 Replies

5. Shell Programming and Scripting

need an explanation on this script...

The following script will create a directory in a directory and will go on as many times as the number you will give in. I am trying to find out how it works ... can someone please help me with that? #!/bin/sh #create a variable and set it to 1 n=1 #start a loop as... (3 Replies)
Discussion started by: I-1
3 Replies

6. Shell Programming and Scripting

Script explanation

#script fileused=test.txt ftp $hostname <<-! > $fileused.err 2>&1 put file.txt /usr/text.txt bye ! kindly the above script the one marked as Bold and underlined as the above i am declaring the new variable as filename ,But when i used i had used as $fileused.err... (1 Reply)
Discussion started by: rajar_r
1 Replies

7. Shell Programming and Scripting

Shell Script Explanation

Hello, I have seen this script on this site. I understand most of it. However I am a bit stuck on the part in red. It appears to be expanding for file in *.zip do zipdir=${file%.*} mkdir $zipdir || echo "unable to create $zipdir" cp $file $zipdir || echo "unable to copy $file"... (3 Replies)
Discussion started by: jaysunn
3 Replies

8. Shell Programming and Scripting

explanation for a script

Guys, was wondering what the meaning of the below bit is ? awk -F ' ' '{print $1 " " $2 ;}' $TEMPFILE | (rm -f $TEMPFILE; sed 's/$/ '"$box"'/g' > $TEMPFILE) Can anyone explain this in detail? what is the significance of rm -f $TEMPFILE here? What all IO/buffering happens here ?How the... (0 Replies)
Discussion started by: hashin_p
0 Replies

9. Shell Programming and Scripting

Explanation of running this script

I have a script that has defined a log file like this. The name of the script is Inside the script there is some thing like this. LOG=/usr/verify TDATE=`date "+%m%d%y"$$` LOGFILE=$LOG.$TDATE. and inside the script it has been written as echo "This is to verify" | tee -a... (2 Replies)
Discussion started by: sendhilmani
2 Replies

10. Shell Programming and Scripting

Script explanation

I have the following script awk '$1 ~ /^*+/ { s += $NF; m++ } END { print NR, m, s } and I use it to get results from the following file A4792 4 COMP9021 5 K9 7 ABC 8 924 1 R2D2 3 (8 Replies)
Discussion started by: sickboy
8 Replies
Login or Register to Ask a Question
cut(1)							      General Commands Manual							    cut(1)

       cut - cut out selected fields of each line of a file

       cut -clist [file1 file2...]
       cut -flist [-dchar] [-s] [file1 file2...]

       Use  the  command to cut out columns from a table or fields from each line of a file.  The fields as specified by list can be fixed length,
       that is, character positions as on a punched card (-c option), or the length can vary from line to line and be marked with a  field  delim-
       iter character like tab (-f option).  The command can be used as a filter.  If no files are given, the standard input is used.

       Use to make horizontal ``cuts'' (by context) through a file, or to put files together in columns.  To reorder columns in a table, use and

       list	   Specifies  ranges  that must be a comma-separated list of integer field numbers in increasing order.  With optional - indicates
		   ranges as in the -o option of nroff/troff for page ranges; for example, 1,4,7; 1-3,8; -5,10 (short for 1-5,10);  or	3-  (short
		   for third through last field).

       -clist	   Specifies character positions to be cut out.  For example, -c1-72 would pass the first 72 characters of each line.

       -flist	   Specifies  the  fields  to be cut out.  For example, -f1,7 copies the first and seventh field only.	Lines with no field delim-
		   iters are passed through intact (useful for table subheadings), unless -s is specified.

       -dchar	   Uses the specified character as the field delimiter.  Default is tab.  Space or other characters with special  meaning  to  the
		   shell must be quoted.  The -d option is used only in combination with the -f option, according to XPG3 and SVID2/SVID3.

       -s	   Suppresses  lines  with  no	delimiter  characters.	 Unless  specified, lines with no delimiters are passed through untouched.
		   Either the -c or -f option must be specified.

       Mapping of user IDs to names:
       cut -d: -f1,5 /etc/passwd
       To set name to the current login name for the csh shell:
       set name=`who am i | cut -f1 -d" "`
       To set name to the current login name for the sh, sh5, and ksh shells:
       name=`who am i | cut -f1 -d" "`

       "line too long"	   A line can have no more than 511 characters or fields.

       "bad list for c/f option"
			   Missing -c or -f option or incorrectly specified list.  No error occurs if a line has fewer fields than the list  calls

       "no fields"	   The list is empty.

See Also
       grep(1), paste(1)