Syntax And Usages

if [ x"$@" = x"" ] ; then cmtc='-nc' ; elif ...; then ...; else cmtc='-c'; fi
if diff -wu f1 f2 > $tf.diff 2>&1; then echo a; else echo b; fi

for ii in `jot $n`; do
for attr in 0 1 4 5 7 ; do

while [ "${DIRSTACK[1]}" ] ; do popd +1 > /dev/null 2>&1 ; done

while expr `netstat -a | grep ":www" | wc -l` '>' $ipm ; do :; done
while :; do ...

while read line; do
        echo postinstall: $line
done

/usr/bin/cal |
  # bold today
  sed -e "s/^/ /; s/$/ /; s/ $4 /$bold $4 $unbold/"

condition_yes && condition_no || echo ok

condition_yes && ! condition_no && echo ok

condition1 && condition2 && echo ok

$ set -x

$ true && true && echo ok
+ true
+ true
+ echo ok
ok

$ false && true && echo ok
+ false

$ true && false && echo ok
+ true
+ false

$ true && false || echo ok
+ true
+ false
+ echo ok
ok

$ false && true || echo ok
+ false
+ echo ok
ok

 case @$1 in @-*) flag=$1; shift;; esac

while list do list done
until list do list done

$ [ -f TiOn.txt ] && { echo a; echo b; }
[ -f TiOn.txt ] && { echo a; echo b; }
+ '[' -f TiOn.txt ']'
+ echo a
a
+ echo b
b

'(echo $pwd_base; echo $pwd; echo *)'
'{ echo $pwd_base; echo $pwd; echo *;}'

$ [ -f TiOn.txt ] && { echo a; echo b }
[ -f TiOn.txt ] && { echo a; echo b }
>

$ [ -f TiOn.txt ] && { echo a; echo b;}
[ -f TiOn.txt ] && { echo a; echo b;}
+ '[' -f TiOn.txt ']'
+ echo a
a
+ echo b
b

l(){  if [ "$TERM" = 'xterm' ]; then echo aaa; fi; }

$ if [ "$TERM" = 'xterm' ]; then echo aaa; fi
aaa

l(){  if [ "$TERM" = 'xterm' ]; then echo aaa; fi }

 l(){
  if [ "$TERM" = 'xterm' ]; then echo aaa; fi
}

l(){
 if [ "$TERM" = 'xterm' ]; then echo aaa; fi }

 l(){  if [ "$TERM" = 'xterm' ]; then echo aaa; fi
}

l(){  if [ "$TERM" = 'xterm' ]; then echo aaa; fi; }

# return the status of last executed command
return $?                     # 0: success, others: failure

grep ...
return $?                     # 0: found, 1:no found

[ $? -ne 0 ] && failure_handling

funcdemo(){
  # Demostrate how a function returns string instead of
  # returning value
  echo "somthing about $1 and $2"
}

result=`funcdemo aaa bbb`

sh: if [ -t 0 ]; then ... fi
C: if(isatty(0)) { ... }

csh
    Some versions have system-wide .cshrc and .login files.  Every
    version puts them in different places.

Start-up (in this order):
    .cshrc   - always; unless the -f option is used.
    .login   - login shells.

Upon termination:
    .logout  - login shells.

Others:
    .history - saves the history (based on $savehist).

tcsh
    Start-up (in this order):
        /etc/csh.cshrc - always.
        /etc/csh.login - login shells.
        .tcshrc        - always.
        .cshrc         - if no .tcshrc was present.
        .login         - login shells

Upon termination:
    .logout        - login shells.

Others:
    .history       - saves the history (based on $savehist).
    .cshdirs       - saves the directory stack.

sh
    Start-up (in this order):
        /etc/profile - login shells.
        .profile     - login shells.

Upon termination:
    any command (or script) specified using the command:
       trap "command" 0

ksh
    Start-up (in this order):
        /etc/profile - login shells.
        .profile     - login shells; unless the -p option is used.
        $ENV         - always, if it is set; unless the -p option is used.
                    /etc/suid_profile - when the -p option is used.

Upon termination:
    any command (or script) specified using the command:
       trap "command" 0

bash
    Start-up (in this order):
        /etc/profile  - login shells.
        .bash_profile - login shells.
        .profile      - login if no .bash_profile is present.
        .bashrc       - interactive non-login shells.
        $ENV          - always, if it is set.

Upon termination:
    .bash_logout  - login shells.

Others:
    .inputrc      - Readline initialization.

$ type eval
eval is a shell builtin

cmd='cat -n'
$ echo aaa | $cmd
     1  aaa

cmd='echo $$; cat -n'
$ echo aaa | $cmd
$$; cat -n

cmd='{ echo $$; cat -n; }'
$ echo aaa | $cmd
bash: {: command not found

cmd='cat -n; echo $$; '
echo aaa | $cmd
+ echo aaa
+ cat '-n;' echo '$$;'
cat: invalid option -- ;

: Can anyone find an example in which eval would make a difference in this
: code:

: a)
:        read -r cmd < $cmdlist
:        eval "$cmd"
: b)
:        read -r cmd  < $cmdlist
:        $cmd

#!/bin/sh

cat > foo.$$ <<-eof
echo a| echo b
eof

cmdlist=foo.$$

echo eval
read cmd < $cmdlist
eval "$cmd"

echo \!eval
read cmd < $cmdlist
$cmd

rm foo.$$

# gives:
#
eval
b
!eval
a| echo b

>How can I use "heredoc" to list something and then feed it into a pipe,

cat <<EOF | xargs -i echo {} {}
file1
file2
file3
EOF

{ cat <<EOF
file1
file2
file3
EOF
} | xargs -i echo {} {}

Newsgroups: comp.unix.shell

>I came across the following usage:
>
>LD_LIBRARY_PATH=... soffice
>
>which set a vriable before running a program.
>
>Can you explain it a little bit? I.e., the syntax, where to use,
>where to find man...

If no  command  name  results,  the  variable  assignments
affect  the  current  shell  environment.   Otherwise, the
variables are added to the  environment  of  the  executed
command  and  do not affect the current shell environment.

Newsgroups: comp.unix.shell

 > I want to pass a swich taken from command line into subroutines.
 > E.g, for the following code, I want to pass the command line swich
 > -t and its parameter into sub2:
[snip]
 > You can see, the first time it works fine, but the second time it is
 > not. and the output of the echo (with "!!" as comment) is wrong too.
 >
 > The reson I can't pass directy is that I also want to do some
 > processing along the passing. This is a general question about how
 > to pass swithes along to subroutines with proper quoting and in
 > proper way.

>sub1(){
>
>  [ "x$1" = "x-t" ] && {
>    file_title_s="-t '$2'"
>    shift 2
>    }
>  sub2 $file_title_s "$@" more from sub1
>}

sub1(){
  case $1 in
   -t) file_title_s=-t
       file_title_o=$2
       shift 2 ;;
  esac
  sub2 "$file_title_s" "$file_title_o" "$@" more from sub1
}

eval set -- $file_title_s "$@"
  sub1 $file_title_s more parameters

$ sh -x test_script0 -t "This is a test" 2nd 3rd
+ [ x-t = x-t ]
file_title_s=-t 'This is a test'
+ shift 2
+ sub1 -t 'This is a test' more parameters
+ echo sub1:7
sub1:7
+ [ x-t = x-t ]
file_title_s=-t "'This"
+ shift 2
args=
args= "is"
args= "is" "a"
args= "is" "a" "test'"
args= "is" "a" "test'" "more"
args= "is" "a" "test'" "more" "parameters"
+ eval set -- -t "'This" "is" "a" "test'" "more" "parameters"
+ set -- -t 'This is a test' more parameters
+ sub2 -t 'This is a test' more parameters 5 6
+ [ x-t = x-t ]
file_title='This
+ shift 2

> Is there any way to nest backticks? What I mean is follows:
> localhost% echo "You have `expr `frm | wc -l` - 1` messages."

#!/bin/sh
echo "You have `expr \`frm | wc -l\` - 1` messages."

$ echo "You have $(expr $(frm | wc -l) -1) messages."

$ echo You have $(expr $(frm | wc -l) - 1) messages.

> Are there any differences between $() and backticks, except from how easy
> they are to nest?

$ set -vx

$ echo `/bin/echo \`pwd\` `
echo `/bin/echo \`pwd\` `
/bin/echo `pwd`
pwd
+++ pwd
++ /bin/echo /home/users/tongsun/txtHist
+ echo /home/users/tongsun/txtHist
/home/users/tongsun/txtHist

$ echo `/bin/echo  \`basename \\\`pwd\\\`\` `
echo `/bin/echo  \`basename \\\`pwd\\\`\` `
/bin/echo  `basename \`pwd\``
basename `pwd`
pwd
++++ pwd
+++ basename /home/users/tongsun/txtHist
++ /bin/echo txtHist
+ echo txtHist
txtHist

$ echo $(/bin/echo  $(basename $(pwd)))
echo $(/bin/echo  $(basename $(pwd)))
/bin/echo  $(basename $(pwd))
basename $(pwd)
pwd
++++ pwd
+++ basename /home/users/tongsun/txtHist
++ /bin/echo txtHist
+ echo txtHist
txtHist

> How can I specify two (or more) commands for xargs. E.g.:
> How can i make the two echo both work for the following command:
> ls | xargs -i echo {}\; echo {} {}

ls | xargs -i sh -c 'echo {};echo {} {}'

>I'm trying to do, I have a list of users that I need to send an email
>to in a file. the problem is that I need to customize the subject
>line.  so what the input file looks like is this:
>
>email <tab> subject <cr>
>email <tab> subject <cr>
>...
>
>I want to loop through the file and use the mail command
>
>mail $email -s $subject < email.txt

while read email subject; do
  mail -s "$subject" "$email" <email.txt
done <input_file

> Does unix has a EOF char, like DOS does? How can I emulate an ^D by
> program?

> > read all my variables < my.input.file
> >
> > If you need to read several lines, use exec:
> >
> > exec 3<&0    # save old stdin to unused file descriptor 3
> > exec < my.input.file  # make my.input.file stdin
> > read line1
> > read line2
> > read line3
> > exec <&3    # get back original stdin
> > exec 3<&-   # and close fd 3.
>
>Thanx, that will work.
>
> > > There is redirection to duplicate input or output to some file
> > > descriptor (10<inpfn , 11>outpfn), but I do have no clue whatsoever what
> > > these file descriptors are used for and how.
> >
> > 0 is stdin, 1 is stdout, and 2 is stderr.  The rest are yours to
> > play with as you need.
>
>That's what I thought, but what can you do with them?  None of the bash
>commands uses a file descriptor as argument.  In the example you give,
>you use them as a temp var to store the standard I/O files.  Is there
>anything else?

exec 10< datafile

read var1 var2 var3 ... <&10

Newsgroups: comp.unix.shell

> I have a row of characters separated by a '+'  ...like so:
>
> bob+smith+william ghol+steve
>
> How can I split the columns and assign each of them to variables.
> into this
>
> var1=bob
> var2=smith
> var3="wiliam ghol"
> var4=steve

#!/bin/sh
x='bob+smith+william ghol+steve'
OLD_IFS=$IFS    # save internal field separator
IFS="+"         # set it to '+'
set -- $x       # make the result positional parameters
IFS=$OLD_IFS    # restore IFS
var1=$1
var2=$2
var3=$3
var4=$4
echo var1=$var1
echo var2=$var2
echo var3=$var3
echo var4=$var4

var1=bob
var2=smith
var3=william ghol
var4=steve

$ cat file
bob+smith+william ghol+steve
$ IFS=+ read var1 var2 var3 var4 <file
$ set |grep '^var.='
var1=bob
var2=smith
var3='william ghol'
var4=steve
$

echo 'a1 b2 c3' | IFS=' ' read var1 var2 var3 var4

$ set |grep '^var.='

echo 'a1 b2 c3' > $tf
IFS=' ' read var1 var2 var3 var4 < $tf

$ set |grep '^var.='
var1=a1
var2=b2
var3=c3
var4=

# reset vars 1st
$ jot -s ' ' 3 | tee $tf
1 2 3

$ IFS=' ' read var1 var2 var3 var4 < $tf

$ set |grep '^var.='
var1=1
var2=2
var3=3
var4=

export var1 var2 var3
echo 'a1 b2 c3' | IFS=' ' read var1 var2 var3 var4

$ set |grep '^var.='
var1=1
var2=2

q="bob+smith+william ghol+steve"

n=0
IFS="+"
for v in $q
do
    n=`expr $n + 1`
    if expr "$v" : '.* .*' > /dev/null
    then
        z="var$n=\"$v\""
    else
        z="var$n=$v"
    fi
    eval "$z"
done

q="bob+smith+william ghol+steve"
oldIFS=$IFS
IFS="+"
var=($q) ## var=(${q// /\ }) # to escape spaces (use \\ on command line)
IFS="$oldIFS"

$ echo ${var[2]}
william ghol

>I need to do the following
>
>for x in $(cat filename)
>do
>    do anything here with the single lines of the file
>done
>
>This works well if there are no spaces in the lines.
>
>How can i set the IFS variable to separate the input only in case of
>newlines.
>
>but this starts a new shell and I loose the value of the variables I set in
>the loop when I come back ( or is there a way to give them back ?

# possible solution . . .
IFSTEMP=${IFS}
IFS=^M
# put as little code as possible in here . . .

#
IFS=${IFSTEMP}

$ printf 'a\x41G\xa0M'
aAG M

$ touch `printf 'a\x41G\xa0M'`
$ diron
-rw-rw-r--    1 tong     tong            0 Sep  8 23:48 aAG?M

> Has anyone written shell scripts that can be translated into non-English
> languages?  I am only interested in translation for prompts and

> I need to write a program that will basically hit the web site and
> return a value to a log...Thought of using a call to lynx, but wasn't
> sure how to determine success or failure

while sleep 30 ; do
    lynx -head -dump http://www.yoursite.com
    if [ $? -ne 0 ] ; then
        logger "Web site is down."
    fi
done &

Newsgroups: comp.unix.shell

> > > What exactly does export mean? I mean, does it like kind of declaration
> > > or something?
> > >
> > > What the impact would it be if the order of setting and exporting
> > > is different.
> > >
> > > Let me explain with examples:
> > >
> > > # case 1
> > > export PS1
> > > PS1='$ '
> > >
> > > # case 2
> > > PS1='$ '
> > > export PS1
> > >
> > > # case 3
> > > PS1='$ '
> > > export PS1
> > > PS1='# '
> > >
> > > what is the system status for above 3 cases. Thanks
> >
> > They all end up being the same in the end.  An export means to make
> > the variable available to all child processes.  Without the export,
> > the child process won't inherit the parents nonexported variables.
> > Since you are all in the one process setting the PS1 and exporting
> > it, all 3 will export the variable to the children.  The export also
> > only needs to be executed once, just like typeset -x.  So for your
> > third example, where you change the value of PS1 after the export,
> > the variable is STILL exported so the new value will be used by the
> > children called after that point.
>
> So I thought. I never thought something else until I used bash2.03
> in linux debian.
>
> bash-2.03$ set | grep PS1
> PS1='\s-\v\$ '
> bash-2.03$ env | grep PS1
> bash-2.03$ export PS1
> bash-2.03$ env | grep PS1
> PS1=\s-\v\$

> so far so good...
>
> bash-2.03$ sh -c 'echo $PS1'
>
> bash-2.03$
>
> and, now, why the sub-process 'sh' didn't get the variable? Does it
> mean bash for debian is different? I tested on Solaris and it worked
> as I expected (PS1 get printed).

bash$ ls -l $(cat /etc/shells) $(command -v ksh) $(command -v bash)
-r-xr-xr-x   1 bin      bin       151976 Oct  6  1998 /bin/csh*
-r-xr-xr-x   3 bin      root       91668 Oct  6  1998 /bin/sh*
-r-xr-xr-x   2 bin      root      257444 Sep  1  1998 /sbin/sh*
-r-xr-xr-x   1 bin      bin       151976 Oct  6  1998 /usr/bin/csh*
-r-xr-xr-x   2 bin      bin       192764 Oct  6  1998 /usr/bin/ksh*
-r-xr-xr-x   3 bin      root       91668 Oct  6  1998 /usr/bin/sh*
-rwxr-xr-x   1 gnu      gnu       606724 Dec 18  1996 /usr/local/bin/bash*

[me@machine me]$ sh -c 'echo $PS1'

[me@machine me]$ ksh -c 'echo $PS1'

[me@machine me]$ bash -c 'echo $PS1'
[\u@\h \W]$

[me@machine me]$ ksh -c 'PS1="hello >" ; echo $PS1'
hello >
[me@machine me]$ sh -c 'PS1="hello >" ; echo $PS1'
hello >
[me@machine me]$ bash -c 'PS1="hello >" ; echo $PS1'
hello >

sh -c 'export PS1="hello >" ; echo $PS1'

[me@machine me]$ PSTEST="hello >"
[me@machine me]$ bash -c 'echo $PSTEST'

[me@machine me]$ export PSTEST="hello >"
[me@machine me]$ bash -c 'echo $PSTEST'
hello >

[me@machine me]$ export PS1="$(echo $PS1)"
[me@machine me]$ksh -c 'echo $PS1'
[\u@\h \W]$
[me@machine me]$sh -c 'echo $PS1'
[\u@\h \W]$
[me@machine me]$bash -c 'echo $PS1'
[\u@\h \W]$

|>>> What exactly does export mean? I mean, does it like kind of declaration
|>>> or something?
|>>>
|>>> What the impact would it be if the order of setting and exporting
|>>> is different.

|> bash-2.03$ set | grep PS1
|> PS1='\s-\v\$ '
|> bash-2.03$ env | grep PS1
|> bash-2.03$ export PS1
|> bash-2.03$ env | grep PS1
|> PS1=\s-\v\$
|
| Whay are you using 'env' with bash? env is a csh-ism (actaully usually a
| separate command, e.g. /usr/bin/env). Use export.

| Note that sh _doesn't appear_ to be ksh (diff reportes them as being
| different too: well it would really, since it comapares file size
| first). I *think* that sh is an original version of Bourne.

| ... The PS1 variable is a special case though, as it is automatically
| exported by the shell, ...

$ unset PS1
$ PS1='CMD> '
CMD> printenv PS1
CMD>

>and, now, why the sub-process 'sh' didn't get the variable? Does it
>mean bash for debian is different?

> ps -fu $1 | awk  '{print $2}'
>
> PID
> 1034
> 4290
>
> What's an easy way to eliminate the heading-string (PID)

True=nonzero,  false = 0
NR = record (line) number (begins at 1)

ps -fu $1 | awk  'NR > 1 {print $2}' > user_proc

Newsgroups: comp.unix.shell

> typeset -i i=0
> while [ "$i" -lt 10 ]; do
>    <command>
>    let i=i+1
> done
>
> "((i=i+1))" or "let i+=1" are alternative syntaxes for the 4th line that may
> also work in bash.

#!/bin/bash
i=0
while [ "$i" -lt 10 ]
do
        <command block>
        i=`expr $i + 1`
done

integer i
for ((i=0; i<10; i++))
do     ...
done

alias integer='typeset -i'

host:~/ndl>echo a > a
host:~/ndl>echo a > b
host:~/ndl>cat a b >a
cat: a: input file is output file

host:~/ndl>cat b >>a
host:~/ndl>cat a
a
a