I know there's a large number of posts on this, I have read a number of them. But unable to find specifics.
Scrutinizer showed me a nice trick using IFS in a while loop in a BASH script, however when I went to hand in my work my tutor informed me that the criteria specifically states SHell script only, he also said I was "unable to do that" in regard to IFS. Looking through his examples in notes, it's all stuck in variable OLDIFS as per usual. My only problem is that I'm using that to parse a file in a while loop which then proceeds to call a number of functions.
So I am uncertain where to change my variable back to the old ifs, as so far I have tried different parts of my loop at the end of loop (which happens to be end of script) and the only other way I can see this working is if I change the variable at the start of each function. So I would have 8 declarations of IFS=$OLDIFS. And there's no guarantee that once i change it back to the OLDIFS in one function, once that function is complete and it enters back into my while loop that it will continue using the new IFS, so I would have to have another 8 declarations of OLDIFS=$IFS; IFS=":\n" at the end of each function as well...
the IFS=":\n" is only messing with my n's in my variable output eg: my add successful statement:
ADDEDPROD="new product added sucessfully"
comes out as " ew product added successfully"
and error for delete.
"unable to delete product, does not exist in database"
"u able to delete product, does ot exist in database"
and a few other error/output variables, everything else seems to work fine eg. Unix tools...
would be good if there was a way around this, anyone know?
or will i just have to change IFS back to OLDIFS at the start and end of every function?
another cygwin only related question for those that use it is, is there anyway to specify to use a SH script? because I tried with the IFS in while loop running in sh by just using
Code:
sh ./script
however this seemed to work fine, so either the cygwin shell script isn't close enough to bourne shell, or the above line didn't open a new 'sh' shell or my teacher is misinformed. (i doubt that last part, but he is still human... I think )
Code:
tr '[:lower:]' '[:upper:]' < $file |
while IFS=: read cmd arg1 arg2 arg3; do
case $cmd in
ADD) add "$arg1" "$arg2" "$arg3"
;;
DELETE) delete "$arg1" "$arg2"
;;
DISPLAYALL) displayall
;;
BRAND) fbrand "$arg1"
;;
PRODUCT) fproduct "$arg1"
;;
*) echo "operation unknown"
;;
esac
done
# this seems to be the only declaration that works in either shell
Code:
#this one gives me errors, but is apprently the right way to do it for bourne shell.
OLDIFS=$IFS
IFS=":\n"
tr '[:lower:]' '[:upper:]' < $file |
while read cmd arg1 arg2 arg3
do
...
.......
...
done
Hi all,
Ok os heres my situation. I have created a database style program that stores a persons info (name,address,phone number etc.) in a file ("database"). after i read in all the values above, i assign them to a line variable:
line="$name^$address^$phonenum" >> phonebuk
as you can see... (1 Reply)
Hi!
I am working in korn shell. I want to reset the dimiliter for the set command to "|" but instead of a command prompt return I am getting something as below
After issuing the command I am getting this....as if the shell is expecting something else. Can anybody suggest what's the problem.
... (2 Replies)
Hi,
This is out of curiosity:
I wanted to extract year, month and date from a variable, and thought that combining read and IFS would help, but this doesn't work:
echo "2010 10 12" | read y m d
I could extract the parts of the date when separated by a -, and setting IFS in a subshell:
... (3 Replies)
Given the scenario like this, if at all if have to use IFS on the below given example, how it should be used.
IFS=/
eg:
/xyz/123/348/file1
I want to use the last slash /file1 . So can anyone, suggest me how to pick the last "/" as a IFS. (4 Replies)
Hi,
while ; do
echo "Please enter "
read enter
yyyy=${enter:0:4}
mm=${enter:5:2}
dd=${enter:8:2}
result=`validateDate $yyyy $mm $dd`
When does the loop keeping repeating till?? till 1 is equal to 1?
what does this mean "${enter:0:4}" .The 0 and 4 part??
... (3 Replies)
hi I keep getting an error with this nested if statement and am getting the error unexpected end of file, can anyone help me as to why this wont execute?
#!/bin/bash
#script to check wether the -i -v statements run correctly
removeFile ()
{
mv $1 $HOME/deleted
}... (3 Replies)
I am using bash and resetting IFS as below when reading the command line arguments. I do this so I can call my script as in Ex1.
Ex1: ./synt2d-ray3dmod.bash --xsrc=12/20/30
This allows me to split both sides so that when I do "shift"
I can get 12/20/30
What I do not understand is... (21 Replies)
Hi ,
i am in my initial learning phase of unix. i was going thru the function part.
below is the example which was there but i am not able to understand logic and the use of IFS(internal field separator)
lspath() {
OLDIFS="$IFS"
IFS=:
for DIR in $PATH ; do echo $DIR ; done
IFS="$OLDIFS"... (8 Replies)
Discussion started by: scriptor
8 Replies
LEARN ABOUT X11R4
read
read(1) User Commands read(1)NAME
read - read a line from standard input
SYNOPSIS
/usr/bin/read [-r] var...
sh
read name...
csh
set variable = $<
ksh
read [ -prsu [n]] [ name ? prompt] [name...]
DESCRIPTION
/usr/bin/read
The read utility will read a single line from standard input.
By default, unless the -r option is specified, backslash () acts as an escape character. If standard input is a terminal device and the
invoking shell is interactive, read will prompt for a continuation line when:
o The shell reads an input line ending with a backslash, unless the -r option is specified.
o A here-document is not terminated after a NEWLINE character is entered.
The line will be split into fields as in the shell. The first field will be assigned to the first variable var, the second field to the
second variable var, and so forth. If there are fewer var operands specified than there are fields, the leftover fields and their interven-
ing separators will be assigned to the last var. If there are fewer fields than vars, the remaining vars will be set to empty strings.
The setting of variables specified by the var operands will affect the current shell execution environment. If it is called in a subshell
or separate utility execution environment, such as one of the following:
(read foo)
nohup read ...
find . -exec read ... ;
it will not affect the shell variables in the caller's environment.
The standard input must be a text file.
sh
One line is read from the standard input and, using the internal field separator, IFS (normally space or tab), to delimit word boundaries,
the first word is assigned to the first name, the second word to the second name, and so on, with leftover words assigned to the last name.
Lines can be continued using
ewline. Characters other than NEWLINE can be quoted by preceding them with a backslash. These backslashes
are removed before words are assigned to names, and no interpretation is done on the character that follows the backslash. The return code
is 0, unless an end-of-file is encountered.
csh
The notation:
set variable = $<
loads one line of standard input as the value for variable. (See csh(1)).
ksh
The shell input mechanism. One line is read and is broken up into fields using the characters in IFS as separators. The escape character,
(), is used to remove any special meaning for the next character and for line continuation. In raw mode, -r, the character is not
treated specially. The first field is assigned to the first name, the second field to the second name, and so on, with leftover fields
assigned to the last name. The -p option causes the input line to be taken from the input pipe of a process spawned by the shell using |&.
If the -s flag is present, the input will be saved as a command in the history file. The flag -u can be used to specify a one digit file
descriptor unit n to read from. The file descriptor can be opened with the exec special command. The default value of n is 0. If name is
omitted, REPLY is used as the default name. The exit status is 0 unless the input file is not open for reading or an end-of-file is encoun-
tered. An end-of-file with the -p option causes cleanup for this process so that another can be spawned. If the first argument contains a
?, the remainder of this word is used as a prompt on standard error when the shell is interactive. The exit status is 0 unless an end-of-
file is encountered.
OPTIONS
The following option is supported:
-r Does not treat a backslash character in any special way. Considers each backslash to be part of the input line.
OPERANDS
The following operand is supported:
var The name of an existing or non-existing shell variable.
EXAMPLES
Example 1: An example of the read command
The following example for /usr/bin/read prints a file with the first field of each line moved to the end of the line:
example% while read -r xx yy
do
printf "%s %s
" "$yy" "$xx"
done < input_file
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables that affect the execution of read: LANG, LC_ALL, LC_CTYPE, LC_MES-
SAGES, and NLSPATH.
IFS Determines the internal field separators used to delimit fields.
PS2 Provides the prompt string that an interactive shell will write to standard error when a line ending with a backslash is read and
the -r option was not specified, or if a here-document is not terminated after a newline character is entered.
EXIT STATUS
The following exit values are returned:
0 Successful completion.
>0 End-of-file was detected or an error occurred.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWcsu |
+-----------------------------+-----------------------------+
|Interface Stability |Standard |
+-----------------------------+-----------------------------+
SEE ALSO csh(1), ksh(1), line(1), set(1), sh(1), attributes(5), environ(5), standards(5)SunOS 5.10 28 Mar 1995 read(1)
11-30-2009
)