Parsing arguments for your shell script

Suppose you want to have some options on your bash shell script, some flags that you can use to alter its behavior. You could do the parsing directly, using ${#} to tell you how many arguments have been supplied, and testing ${1:0:1} to test the first character of the first argument to see if it is a minus sign. You would need some if/then or case logic to identify which option it is and whether it takes an argument. What if the user doesn't supply a required argument? What if the user calls your script with two options combined (e.g., -ab)? Will you also parse for that? The need to parse options for a shell script is a common situation. Lots of scripts have options. Isn't there a more standard way to do this?

This article is excerpted from the newly published book bash Cookbook.

The solution -- use bash's built-in getopts command to help parse options. Here is an example, based largely on the example in the manpage for getopts

 #!/usr/bin/env bash
 # cookbook filename: getopts_example
 #
 # using getopts
 #
 aflag=
 bflag=
 while getopts 'ab:' OPTION
 do
   case $OPTION in
   a) aflag=1
   ;;
   b) bflag=1
   bval="$OPTARG"
   ;;
   ?) printf "Usage: %s: [-a] [-b value] args\n" $(basename $0) >&2
   exit 2
   ;;
   esac
 done
 shift $(($OPTIND - 1))

 if [ "$aflag" ]
 then
   printf "Option -a specified\n"
 fi
 if [ "$bflag" ]
 then
   printf 'Option -b "%s" specified\n' "$bval"
 fi
 printf "Remaining arguments are: %s\n" "$*"

There are two kinds of options supported here. The first and simpler kind is an option that stands alone. It typically represents a flag to modify a command's behavior. An example of this sort of option is the -l option on the ls command. The second kind of option requires an argument. An example of this is the mysql command's -u option, which requires that a username be supplied, as in mysql -u sysadmin. Let's look at how getopts supports the parsing of both kinds.

The use of getopts has two arguments.

 getopts 'ab:' OPTION

The first is a list of option letters. The second is the name of a shell variable. In our example, we are defining -a and -b as the only two valid options, so the first argument in getopts has just those two letters -- and a colon. What does the colon signify? It indicates that -b needs an argument, just like -u username or -f filename might be used. The colon needs to be adjacent to any option letter taking an argument. For example, if only -a took an argument we would need to write 'a:b' instead.

The getopts built-in will set the variable named in the second argument to the value that it finds when it parses the shell script's argument list ($1, $2, etc.). If it finds an argument with a leading minus sign, it will treat that as an option argument and put the letter into the given variable ($OPTION in our example). Then it returns true (i.e., 0) so that the while loop will process the option then continue to parse options by repeated calls to getopts until it runs out of arguments (or encounters a double minus -- to allow users to put an explicit end to the options). Then getopts returns false (i.e., non-zero) and the while loop ends.

Inside the loop, when the parsing has found an option letter for processing, we use a case statement on the variable $OPTION to set flags or otherwise take action when the option is encountered. For options that take arguments, that argument is placed in the shell variable $OPTARG (a fixed name not related to our use of $OPTION as our variable). We need to save that value by assigning it to another variable because as the parsing continues to loop, the variable $OPTARG will be reset on each call to getopts.

The third case of our case statement is a question mark, a shell pattern that matches any single character. When getopts finds an option that is not in the set of expected options ('ab:' in our example) then it will return a literal question mark in the variable ($OPTION in our example). So we could have made our case statement read \?) or '?') for an exact match, but the ? as a pattern match of any single character provides a convenient default for our case statement. It will match a literal question mark as well as matching any other single character.

In the usage message that we print, we have made two changes from the example script in the manpage. First, we use $(basename $0) to give the name of the script without all the extra pathnames that may have been part of how it was invoked. Secondly, we redirect this message to standard error (>&2) because that is really where such messages belong. All of the error messages from getopts that occur when an unknown option or missing argument is encountered are always written to standard error. We add our usage message to that chorus.

When the while loop terminates, we see the next line to be executed is:

 shift $(($OPTIND - 1))

which is a shift statement used to move the positional parameters of the shell script from $1, $2, etc. down a given number of positions (tossing the lower ones). The variable $OPTIND is an index into the arguments that getopts uses to keep track of where it is when it parses. Once we are done parsing, we can toss all the options that we've processed by doing this shift statement. For example, if we had this command line:

 myscript -a -b alt plow harvest reap

then after parsing for options, $OPTIND would be set to 4. By doing a shift of three ($OPTIND-1) we would get rid of the options and then a quick echo$* would give this:

 plow harvest reap

So, the remaining (non-option) arguments are ready for use in your script (in a for loop perhaps). In our example script, the last line is a printf showing all the remaining arguments.

How to Select Columns From a File?

The cut command takes a vertical slice of a file, printing only the specified columns or fields. Like the sort command, the cut command defines a field as a word set off by blanks, unless you specify your own delimiter. It's easiest to think of a column as just the nth character on each line। In other words, "column 5" consists of the fifth character of each line.


Consider a slight variation on the company.data file we've been playing with in this section:

406378:Sales:Itorre:Jan
031762:Marketing:Nasium:Jim
636496:Research:Ancholie:Mel
396082:Sales:Jucacion:Ed

If you want to print just columns 1 to 6 of each line (the employee serial numbers), use the -c1-6 flag, as in this command:

cut -c1-6 company.data
406378
031762
636496
396082

If you want to print just columns 4 and 8 of each line (the first letter of the department and the fourth digit of the serial number), use the -c4,8 flag, as in this command:

cut -c4,8 company.data
3S
7M
4R
0S

And since this file obviously has fields delimited by colons, we can pick out just the last names by specifying the -d: and -f3 flags, like this:

cut -d: -f4,3 company.data
Itorre
Nasium
Ancholie
Jucacion

Here is a summary of the most common flags for the cut command:

-c [n | n,m | n-m] Specify a single column, multiple columns (separated by a comma), or range of columns (separated by a dash).
-f [n | n,m | n-m] Specify a single field, multiple fields (separated by a comma), or range of fields (separated by a dash).
-dc Specify the field delimiter.
-s Suppress (don't print) lines not containing the delimiter.

find command

find - search for files in a directory hierarchy

SYNOPSIS

find [path...] [expression]

DESCRIPTION

This manual page documents the GNU version of find. find searches the directory tree rooted at each given file name by evaluating the given expression from left to right, according to the rules of precedence (see section OPERATORS), until the outcome is known (the left hand side is false for and operations, true for or), at which point find moves on to the next file name.

The first argument that begins with `-', `(', `)', `,', or `!' is taken to be the beginning of the expression; any arguments before it are paths to search, and any arguments after it are the rest of the expression. If no paths are given, the current directory is used. If no expression is given, the expression `-print' is used.

find exits with status 0 if all files are processed successfully, greater than 0 if errors occur.

EXPRESSIONS

The expression is made up of options (which affect overall operation rather than the processing of a specific file, and always return true), tests (which return a true or false value), and actions (which have side effects and return a true or false value), all separated by operators. -and is assumed where the operator is omitted. If the expression contains no actions other than -prune, -print is performed on all files for which the expression is true.

OPTIONS

All options always return true. They always take effect, rather than being processed only when their place in the expression is reached. Therefore, for clarity, it is best to place them at the beginning of the expression.

-daystart

Measure times (for -amin, -atime, -cmin, -ctime, -mmin, and -mtime) from the beginning of today rather than from 24 hours ago.

-depth

Process each directory's contents before the directory itself.

-follow

Dereference symbolic links. Implies -noleaf.

-help, --help

Print a summary of the command-line usage of find and exit.

-maxdepth levels

Descend at most levels (a non-negative integer) levels of directories below the command line arguments. `-maxdepth 0' means only apply the tests and actions to the command line arguments.

-mindepth levels

Do not apply any tests or actions at levels less than levels (a non-negative integer). `-mindepth 1' means process all files except the command line arguments.

-mount

Don't descend directories on other filesystems. An alternate name for -xdev, for compatibility with some other versions of find.

-noleaf

Do not optimize by assuming that directories contain 2 fewer subdirectories than their hard link count. This option is needed when searching filesystems that do not follow the Unix directory-link convention, such as CD-ROM or MS-DOS filesystems or AFS volume mount points. Each directory on a normal Unix filesystem has at least 2 hard links: its name and its `.' entry. Additionally, its subdirectories (if any) each have a `..' entry linked to that directory. When find is examining a directory, after it has statted 2 fewer subdirectories than the directory's link count, it knows that the rest of the entries in the directory are non-directories (`leaf' files in the directory tree). If only the files' names need to be examined, there is no need to stat them; this gives a significant increase in search speed.

-version, --version

Print the find version number and exit.

-xdev

Don't descend directories on other filesystems.

TESTS

Numeric arguments can be specified as

+n

for greater than n,

-n

for less than n,

n

for exactly n.

-amin n

File was last accessed n minutes ago.

-anewer file

File was last accessed more recently than file was modified. -anewer is affected by -follow only if -follow comes before -anewer on the command line.

-atime n

File was last accessed n*24 hours ago.

-cmin n

File's status was last changed n minutes ago.

-cnewer file

File's status was last changed more recently than file was modified. -cnewer is affected by -follow only if -follow comes before -cnewer on the command line.

-ctime n

File's status was last changed n*24 hours ago.

-empty

File is empty and is either a regular file or a directory.

-false

Always false.

-fstype type

File is on a filesystem of type type. The valid filesystem types vary among different versions of Unix; an incomplete list of filesystem types that are accepted on some version of Unix or another is: ufs, 4.2, 4.3, nfs, tmp, mfs, S51K, S52K. You can use -printf with the %F directive to see the types of your filesystems.

-gid n

File's numeric group ID is n.

-group gname

File belongs to group gname (numeric group ID allowed).

-ilname pattern

Like -lname, but the match is case insensitive.

-iname pattern

Like -name, but the match is case insensitive. For example, the patterns `fo*' and `F??' match the file names `Foo', `FOO', `foo', `fOo', etc.

-inum n

File has inode number n.

-ipath pattern

Like -path, but the match is case insensitive.

-iregex pattern

Like -regex, but the match is case insensitive.

-links n

File has n links.

-lname pattern

File is a symbolic link whose contents match shell pattern pattern. The metacharacters do not treat `/' or `.' specially.

-mmin n

File's data was last modified n minutes ago.

-mtime n

File's data was last modified n*24 hours ago.

-name pattern

Base of file name (the path with the leading directories removed) matches shell pattern pattern. The metacharacters (`*', `?', and `[]') do not match a `.' at the start of the base name. To ignore a directory and the files under it, use -prune; see an example in the description of -path.

-newer file

File was modified more recently than file. -newer is affected by -follow only if -follow comes before -newer on the command line.

-nouser

No user corresponds to file's numeric user ID.

-nogroup

No group corresponds to file's numeric group ID.

-path pattern

File name matches shell pattern pattern. The metacharacters do not treat `/' or `.' specially; so, for example,
find . -path './sr*sc'
will print an entry for a directory called './src/misc' (if one exists). To ignore a whole directory tree, use -prune rather than checking every file in the tree. For example, to skip the directory `src/emacs' and all files and directories under it, and print the names of the other files found, do something like this:
find . -path './src/emacs' -prune -o -print

-perm mode

File's permission bits are exactly mode (octal or symbolic). Symbolic modes use mode 0 as a point of departure.

-perm -mode

All of the permission bits mode are set for the file.

-perm +mode

Any of the permission bits mode are set for the file.

-regex pattern

File name matches regular expression pattern. This is a match on the whole path, not a search. For example, to match a file named `./fubar3', you can use the regular expression `.*bar.' or `.*b.*3', but not `b.*r3'.

-size n[bckw]

File uses n units of space. The units are 512-byte blocks by default or if `b' follows n, bytes if `c' follows n, kilobytes if `k' follows n, or 2-byte words if `w' follows n. The size does not count indirect blocks, but it does count blocks in sparse files that are not actually allocated.

-true

Always true.

-type c

File is of type c:

b

block (buffered) special

c

character (unbuffered) special

d

directory

p

named pipe (FIFO)

f

regular file

l

symbolic link

s

socket

D

door (Solaris)

-uid n

File's numeric user ID is n.

-used n

File was last accessed n days after its status was last changed.

-user uname

File is owned by user uname (numeric user ID allowed).

-xtype c

The same as -type unless the file is a symbolic link. For symbolic links: if -follow has not been given, true if the file is a link to a file of type c; if -follow has been given, true if c is `l'. In other words, for symbolic links, -xtype checks the type of the file that -type does not check.

ACTIONS

-exec command ;

Execute command; true if 0 status is returned. All following arguments to find are taken to be arguments to the command until an argument consisting of `;' is encountered. The string `{}' is replaced by the current file name being processed everywhere it occurs in the arguments to the command, not just in arguments where it is alone, as in some versions of find. Both of these constructions might need to be escaped (with a `\') or quoted to protect them from expansion by the shell. The command is executed in the starting directory.

-fls file

True; like -ls but write to file like -fprint.

-fprint file

True; print the full file name into file file. If file does not exist when find is run, it is created; if it does exist, it is truncated. The file names ``/dev/stdout'' and ``/dev/stderr'' are handled specially; they refer to the standard output and standard error output, respectively.

-fprint0 file

True; like -print0 but write to file like -fprint.

-fprintf file format

True; like -printf but write to file like -fprint.

-ok command ;

Like -exec but ask the user first (on the standard input); if the response does not start with `y' or `Y', do not run the command, and return false.

-print

True; print the full file name on the standard output, followed by a newline.

-print0

True; print the full file name on the standard output, followed by a null character. This allows file names that contain newlines to be correctly interpreted by programs that process the find output.

-printf format

True; print format on the standard output, interpreting `\' escapes and `%' directives. Field widths and precisions can be specified as with the `printf' C function. Unlike -print, -printf does not add a newline at the end of the string. The escapes and directives are:

\a

Alarm bell.

\b

Backspace.

\c

Stop printing from this format immediately and flush the output.

\f

Form feed.

\n

Newline.

\r

Carriage return.

\t

Horizontal tab.

\v

Vertical tab.

\\

A literal backslash (`\').

\NNN

The character whose ASCII code is NNN (octal).

A `\' character followed by any other character is treated as an ordinary character, so they both are printed.

%%

A literal percent sign.

%a

File's last access time in the format returned by the C `ctime' function.

%Ak

File's last access time in the format specified by k, which is either `@' or a directive for the C `strftime' function. The possible values for k are listed below; some of them might not be available on all systems, due to differences in `strftime' between systems.

@

seconds since Jan. 1, 1970, 00:00 GMT.

Time fields:

H

hour (00..23)

I

hour (01..12)

k

hour ( 0..23)

l

hour ( 1..12)

M

minute (00..59)

p

locale's AM or PM

r

time, 12-hour (hh:mm:ss [AP]M)

S

second (00..61)

T

time, 24-hour (hh:mm:ss)

X

locale's time representation (H:M:S)

Z

time zone (e.g., EDT), or nothing if no time zone is determinable

Date fields:

a

locale's abbreviated weekday name (Sun..Sat)

A

locale's full weekday name, variable length (Sunday..Saturday)

b

locale's abbreviated month name (Jan..Dec)

B

locale's full month name, variable length (January..December)

c

locale's date and time (Sat Nov 04 12:02:33 EST 1989)

d

day of month (01..31)

D

date (mm/dd/yy)

h

same as b

j

day of year (001..366)

m

month (01..12)

U

week number of year with Sunday as first day of week (00..53)

w

day of week (0..6)

W

week number of year with Monday as first day of week (00..53)

x

locale's date representation (mm/dd/yy)

y

last two digits of year (00..99)

Y

year (1970...)

%b

File's size in 512-byte blocks (rounded up).

%c

File's last status change time in the format returned by the C `ctime' function.

%Ck

File's last status change time in the format specified by k, which is the same as for %A.

%d

File's depth in the directory tree; 0 means the file is a command line argument.

%f

File's name with any leading directories removed (only the last element).

%F

Type of the filesystem the file is on; this value can be used for -fstype.

%g

File's group name, or numeric group ID if the group has no name.

%G

File's numeric group ID.

%h

Leading directories of file's name (all but the last element).

%H

Command line argument under which file was found.

%i

File's inode number (in decimal).

%k

File's size in 1K blocks (rounded up).

%l

Object of symbolic link (empty string if file is not a symbolic link).

%m

File's permission bits (in octal).

%n

Number of hard links to file.

%p

File's name.

%P

File's name with the name of the command line argument under which it was found removed.

%s

File's size in bytes.

%t

File's last modification time in the format returned by the C `ctime' function.

%Tk

File's last modification time in the format specified by k, which is the same as for %A.

%u

File's user name, or numeric user ID if the user has no name.

%U

File's numeric user ID.

A `%' character followed by any other character is discarded (but the other character is printed).

-prune

If -depth is not given, true; do not descend the current directory.
If -depth is given, false; no effect.

-ls

True; list current file in `ls -dils' format on standard output. The block counts are of 1K blocks, unless the environment variable POSIXLY_CORRECT is set, in which case 512-byte blocks are used.

OPERATORS

Listed in order of decreasing precedence:

( expr )

Force precedence.

! expr

True if expr is false.

-not expr

Same as ! expr.

expr1 expr2

And (implied); expr2 is not evaluated if expr1 is false.

expr1 -a expr2

Same as expr1 expr2.

expr1 -and expr2

Same as expr1 expr2.

expr1 -o expr2

Or; expr2 is not evaluated if expr1 is true.

expr1 -or expr2

Same as expr1 -o expr2.

expr1 , expr2

List; both expr1 and expr2 are always evaluated. The value of expr1 is discarded; the value of the list is the value of expr2.

EXAMPLES

find /home -user joe

Find every file under the directory /home owned by the user joe.

find /usr -name *stat

Find every file under the directory /usr ending in ".stat".

find /var/spool -mtime +60

Find every file under the directory /var/spool that was modified more than 60 days ago.

find /tmp -name core -type f -print | xargs /bin/rm -f

Find files named core in or below the directory /tmp and delete them. Note that this will work incorrectly if there are any filenames containing newlines, single or double quotes, or spaces.

find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f

Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names containing single or double quotes, spaces or newlines are correctly handled. The -name test comes before the -type test in order to avoid having to call stat(2) on every file.

find . -type f -exec file '{}' \;

Runs `file' on every file in or below the current directory. Notice that the braces are enclosed in single quote marks to protect them from interpretation as shell script punctuation. The semicolon is similarly protected by the use of a backslash, though ';' could have been used in that case also.

find /       \( -perm -4000 -fprintf /root/suid.txt '%#m %u %p\n' \) , \
             \( -size +100M -fprintf /root/big.txt  '%-10s %p\n' \)

Traverse the filesystem just once, listing setuid files and directories into /root/suid.txt and large files into /root/big.txt.

find $HOME  -mtime 0

Search for files in your home directory which have been modified in the last twenty-four hours. This command works this way because the time since each file was last modified is divided by 24 hours and any remainder is discarded. That means that to match -mtime

0, a file will have to have a modification in the past which is less than 24 hours ago.

find . -perm 664

Search for files which have read and write permission for their owner, and group, but which other users can read but not write to. Files which meet these criteria but have other permissions bits set (for example if someone can execute the file) will not be matched.

find . -perm -664

Search for files which have read and write permission for their owner and group, and which other users can read, without regard to the presence of any extra permission bits (for example the executable bit). This will match a file which has mode 0777, for example.

find . -perm /222

Search for files which are writable by somebody (their owner, or their group, or anybody else).

find . -perm /220
find . -perm /u+w,g+w
find . -perm /u=w,g=w

All three of these commands do the same thing, but the first one uses the octal representation of the file mode, and the other two use the symbolic form. These commands all search for files which are writable by either their owner or their group. The files don't have to be writable by both the owner and group to be matched; either will do.

find . -perm -220
find . -perm -g+w,u+w

Both these commands do the same thing; search for files which are writable by both their owner and their group.

find . -perm -444 -perm /222 ! -perm /111
find . -perm -a+r -perm /a+w ! -perm /a+x

These two commands both search for files that are readable for everybody (-perm -444 or -perm -a+r), have at least on write bit set (-perm /222 or -perm /a+w) but are not executable for anybody (! -perm /111 and ! -perm /a+x respectively)

Difference Between Static & Global Variable

Variables defined local to a function disappear at the end of the function scope. So when we call the function again, storage for variables is created and values are reinitialized. So if we want the value to be extent throughout the life of a program, we can define the local variable as "static." Initialization is performed only at the first call and data is retained between func calls.

Had it been gloal variable, it would have been available outside the scope of the function, but static variable is not available outside the scope of a function (helpful in localizing errors - as it can't be changed outside the function scope).

Static and global variable differ a lot in their behaviour to life and scope. First, let me distinguish between life and scope. Life of an object determines whether the object is still in the memory (of the process) whereas scope of the object is whether can I know the variable by its name at this position. It is possible that object is live, but not visible (not in scope) but not that object is not alive but in scope (except for dynamically allocated objects where you refer object through pointers).

Static variables are local in scope to their module in which they are defined, but life is throughout the program. Say for a static variable inside a function cannot be called from outside the function (because it's not in scope) but is alive and exists in memory. The next time this function is entered (within the same program) the same chunk of memory would be accessed now retaining the variables old value and no new memory is allocated this time for this variable like other variables in the function (automatic variables). So basically the variable persists throughout the program. Similarly if a static variable is defined in a global space (say at beginning of file) then this variable will be accessible only in this file (file scope).

On the other hand global variables have to be defined globally, persists (life is) throughout the program, scope is also throughout the program. This means such variables can be accessed from any function, any file of the program.

So if you have a global variable and u r distributing ur files as a library and you want others to not access your global variable, you may make it static by just prefixing keyword static (of course if same variable is not required in other files of yours).

Life is beautiful!!! Live it !!!

A Nice Article from the writings of Swami Vivekananda...............

I once had a friend who grew to be very close to me. Once when we were
sitting at the edge of a swimming pool, she filled the palm of her hand
with some water and held it before me, and said this: "You see this water
carefully contained on my hand? It symbolizes Love."

This was how I saw it: As long as you keep your hand caringly open and
allow it to remain there, it will always be there. However, if you attempt to
close your fingers round it and try to posses it, it will spill through the
first cracks it finds.

This is the greatest mistake that people do when they meet love...they try
to posses it, they demand, they expect... and just like the water
spilling out of your hand, love will retrieve from you . For love is meant
to be free, you cannot change its nature. If there are people you love,
allow them to be free beings.

Give and don't expect.
Advise, but don't order.
Ask, but never demand.

It might sound simple, but it is a lesson that may take a lifetime to
truly practice. It is the secret to true love. To truly practice it, you must
sincerely feel no expectations from those who you love, and yet an
unconditional caring."

Passing thought... Life is not measured by the number of breaths we take;
but by the moments that take our breath away.....

Life is beautiful!!! Live it !!!

Transaction Control

You can use two methods to specify the boundaries of transactions with SQL statements. In the most common method,
you specify the start of a multistatement transaction by executing the BEGIN WORK statement. In databases that are created
with the MODE ANSI option, no need exists to mark the beginning of a transaction. One is always in effect;
you indicate only the end of each transaction.

In both methods, to specify the end of a successful transaction, execute the COMMIT WORK statement. This statement tells the database
server that you reached the end of a series of statements that must succeed together. The database server does whatever is necessary
to make sure that all modifications are properly completed and committed to disk.

A program can also cancel a transaction deliberately by executing the ROLLBACK WORK statement. This statement asks the database
server to cancel the current transaction and undo any changes.

Informix SQL Guide

http://www.ics.uci.edu/~dbclass/ics184/htmls/Informix_guide.html

Dynamic SQL - with Informix

• Dynamic SQL allows a program to form an SQL statement during execution, so that the statement can be determined by user input. The action is performed in two steps.

  1. Preparing a statement

     It uses PREPARE statement to have the database server examine the statement text and prepare it for execution.

         EXEC SQL prepare  from '';
     

  2. Executing prepared SQL

     It uses EXECUTE statement to execute the prepared statement.

         EXEC SQL execute  from '';
     

  For instance, if you want to inquire the information of some students, you can use the following dynamic SQL for query:

      EXEC SQL BEGIN DECLARE SECTION;
     int sid;
     char sname[10];
     EXEC SQL END DECLARE SECTION;
  
     EXEC SQL prepare query_stud from 'select id,name from student where name=?';
  
     EXEC SQL execute query_stud into :sid, sname using 'Mike';
     printf("Student: (%d, %s)\n", sid, sname);
  
     EXEC SQL execute query_stud into :sid, sname using 'David';
     printf("Student: (%d, %s)\n", sid, sname);
  

  The above produces the following results:

      Student: (2, Mike)
     Student: (9, David)
  

• Embedded SQL(including cursor)

  SQL statements can be embedded in the C and COBOL program. In C, all the statement is preceded by "EXEC SQL". There is a detail example in the next section.

  A cursor is a special data object that represents the current state of a query. It is used for retrieving multiple resulting rows of query. It is used in 5 steps:

  1. Declaring a Cursor

         EXEC SQL DECLARE  CURSOR FOR ;
     

  2. Opening a Cursor

         EXEC SQL OPEN ;
     

  3. Fetching Rows

         EXEC SQL FETCH ;
     

  4. Closing a Cursor

         EXEC SQL CLOSE ;
     

  5. Freeing a Cursor

         EXEC SQL FREE ;
     

     For instance, the following program lists the information of all students.

         EXEC SQL BEGIN DECLARE SECTION;
        int sid;
        char sname[10];
        EXEC SQL END DECLARE SECTION;
     
        EXEC SQL DECLARE cursor_stud CURSOR FOR select id,name from student;
        EXEC SQL OPEN cursor_stud;
        while ( SQLCODE == 0 ) {
            EXEC SQL OPEN cursor_stud INTO :sid, :sname;
            if ( SQLCODE == 0 )
              printf("Student (%d, %s)\n", sid, sname);
         }
        EXEC SQL CLOSE cursor_stud;
        EXEC SQL FREE cursor_stud;
     

     SQLCODE is set to 0 by the database if the select statement is valid, otherwise set to 100. It is used to detect the end of data.

---

Informix Programming Guide Setting Environment

• setenv INFORMIXSERVER rodan_ius_net
• setenv PATH $INFORMIXDIR/bin:$PATH
• setenv LD_LIBRARY_PATH $INFORMIXDIR/lib:$INFORMIXDIR/lib/esql:$INFORMIXDIR/lib/dmi:$INFORMIXDIR/lib/c++

How do I compile ESQL/C code for use with C++?

There have been a variety of answers, but not any one systematic answer.
Now there is what I believe is a definitive answer -- it's all in the
attached shell archive.

What do you get?
*   Updated ESQL/C prototypes for 4.00, 4.1x, 5.0x and 7.2x
*   An esql++ compiler
*   A pair of patch files for modifying your standard ESQL/C compiler.
   Only use these if your ESQL/C is version 4.1 or 5.x; later versions
   already have the necessary change).
*   A minimal test application.
*   No documentation apart from this message!

What do you need to do?
*   Unpack the shell archive.
*   Place the esql* headers in either $INFORMIXDIR/incl (version 4)
   or $INFORMIXDIR/incl/esql (version 5 or later)
*   Place the esql++ script in $INFORMIXDIR/bin
*   Decide which version of ESQL/C you are using and set the
   ESQLC_VERSION environment variable to a value such as:
   export ESQLC_VERSION=506    # 5.06.UC1
*   Optionally modify esql++ to give the correct default value of
   of ESQLC_VERSION.
*   Decide which C++ compiler you use -- if it isn't CC, set:
   export INFORMIXC=g++
*   Try compiling the test application:
   esql++ -o testapp testmain.ec testsub.ec
*   Run it against your local stores database -- it should say '2'.

What if you can't modify your INFORMIXDIR?
*   Copy $INFORMIXDIR/bin/esql to somewhere where you can modify it
   (eg /some/where/bin/esql)
*   Patch it if necessary.
*   Place the headers in another directory (eg /some/where/include).
*   Modify esql++ so that:
   -- arglist starts of with -I/some/where/include as one component
   -- ESQL defaults to /some/where/bin/esql
*   If you don't have to patch the esql script, you don't have to copy it
   to /some/where/bin and you don't need to make the corresponding
   modification in the esql++ script.

What about other versions of ESQL/C?
*   If you are still using a pre-4.00 version of ESQL/C, the chances are
   that the code which edits the 4.xx code will be useful.  However, the
   prototypes for the ESQL/C interface functions are not known and will
   have to be determined by inspection of the generated code.  Good luck!
   It will probably be easier to upgrade to a later version.
*   I haven't been able to test version 8.xx ESQL/C; it isn't available to
   me.  However, the indications are that it will need the same treatment
   as the other post-5.00 implementations of ESQL/C.
*   Testing with the version 9.10 ESQL/C compiler indicates that this
   script is still necessary.
*   Ideally, you won't need this script at all for post-9.xx versions.  If
   you are using some later version, you will need to revise the script so
   that the case statement on $ESQLC_VERSION handles the new (presumably
   4-digit) version number.
*   Note that ESQL/C 7.24 has some support for C++ built in.  In
   particular, it preprocesses files with the .ecpp extension and then
   compiles them with the C++ compiler.  It may not link the object code
   with the C++ compiler; if it doesn't, you'd have to do that by running
   the link command it with INFORMIXC="C++ compiler" in the environment.

Which versions of ESQL/C are are known to work with this?
*   The code has been tested against Informix-ESQL/C versions 4.12.UC1,
   5.06.UC1, 6.00.UE1, 7.13.UC1, 7.22.UC2, 9.10.UC2 on a Sun Sparc 20
   running Solaris 2.5.1 with both SUNWspro C++ SPARCompiler SC4.0.1 and
   GNU G++ 2.7.2.2.

Are there any known bugs?
*   Life will get very difficult if you pass arguments with quotes or
   spaces in them to your compiler:

       esql++ -DOPENQUOTE="'" -DSOMMAT="string with blanks" thingy.ec

   I do have a solution: it is another program called escape which
   deals with precisely that sort of problem.
       arglist="$arglist `escape $arg`"
   But that requires some more source and isn't generally necessary.
   Also, the underlying esql script does not work reliably with such
   arguments, so the changes needed are even more extensive.

*   The esql7_20.h header is needed until bug B73951 is fixed.

GSM main Features

• Short Message Service which allows you to send and receive 126 character text messages
  
• Ability to use same phone in a number of network-related countries
  
• Allows data transmission and reception across GSM networks at speeds up to 9,600 bps currently
  
• Allows fax transmission and reception across GSM networks at speeds up to 9,600 bps currently
  
• Forwarding of calls to another number
  
• More capacity, ensuring rapid call set-up. Handsets also smaller and more robust.
  
• Talk to a number of other parties simultaneously
  
• Place a call on Hold while you access another call
  
• Notifies you of another call whilst on a call
  
• Encrypted conservations that cannot be tapped
  
• You can barr outgoing calls and incoming calls
  
• CLIP Allows you to see the telephone number of the incoming caller on the LCD screen of the handset
  
• CLIR allows you to bar anyone from seeing your number via CLIP
  
• Real-time call costs on the handsets's LCD screen
  
• Allows location/cell-specific reception of text messages.
  
• Closed User Group - Allows a set of phones to be classed as PBX extensions.
  
• Emergency Calls - In the majority of countries, the global 112 emergency number can be dialled free.
  
• No-static connections