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Full Discussion: Check for File Existence
Operating Systems AIX Check for File Existence Post 302223255 by bakunin on Friday 8th of August 2008 07:30:41 PM
Old 08-08-2008
use the "test" command with the "-f" option. It tests for the existence of a (regular) file. You could even refine your test with the "-r" option, which tests for a regular file which has read access:

Code:
if [ -f /path/to/file ] ; then
     print - "file /path/to/file exists and is a regular file"
else
     print "file /path/to/file does not exist or is no regular file"
fi

if [ -r /path/to/file ] ; then
     print - "file /path/to/file exists and is a readable regular file"
else
     print "file /path/to/file does not exist or is not readable or no regular file"
fi

Employing the logic you use it would be possible to set a flag:

Code:
#! /bin/ksh
typeset -i lFoundSO=0
typeset    fDir="/some/where"
typeset    fFileBuffer=""

ls $fDir/SALESORDER*.dat | while read fFileBuffer ; do
     lFoundSO=1
     do_some_processing $fFileBuffer
done

if [ $lFoundSO eq 1 ] ; then
     ls $fDir/PURCHASEORDER*.dat | while read fFileBuffer ; do
          do_some_other_processing $fFileBuffer
     done
fi

if [ $lFoundSO eq 0 ] ; then
     print -u2 "Error: no SALESORDER-file found"
     exit 1
fi

exit 0

Notice that i have not used a for-loop but a while-loop instead. The reason is that the commandline has a limited length (4096 characters per POSIX 1003). As the wildcards get expanded when processing the commandline it can well be that many matching files would make a string too long for the shell to digest. You would get a "line too long-error". Therefore the while-loop and a pipeline is more safe than the for-loop.

I hope this helps.

bakunin
 

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LEARN ABOUT MOJAVE

function

shell_builtins(1)                                                                                                                shell_builtins(1)

NAME

       shell_builtins, case, for, foreach, function, if, repeat, select, switch, until, while - shell command interpreter built-in commands

       The  shell  command  interpreters  csh(1), ksh(1), and sh(1) have special built-in commands. The commands case, for, foreach, function, if,
       repeat, select, switch, until, and while are commands in the syntax recognized by the shells. They are described in the Commands section of
       the  manual  pages of the respective shells. The remaining commands listed in the table below are built into the shells for reasons such as
       efficiency or data sharing between command invocations. They are described on their respective manual pages.

                                    |
                 Command            |           Shell
       alias                        |csh, ksh
       bg                           |csh, ksh, sh
       break                        |csh, ksh, sh
       case                         |csh, ksh, sh
       cd                           |csh, ksh, sh
       chdir                        |csh, sh
       continue                     |csh, ksh, sh
       dirs                         |csh
       echo                         |csh, ksh, sh
       eval                         |csh, ksh, sh
       exec                         |csh, ksh, sh
       exit                         |csh, ksh, sh
       export                       |ksh, sh
       false                        |ksh
       fc                           |ksh
       fg                           |csh, ksh, sh
       for                          |ksh, sh
       foreach                      |csh
       function                     |ksh
       getopts                      |ksh, sh
       glob                         |csh
       goto                         |csh
       hash                         |ksh, sh
       hashstat                     |csh
       history                      |csh
       if                           |csh, ksh, sh
       jobs                         |csh, ksh, sh
       kill                         |csh, ksh, sh
       let                          |ksh
       limit                        |csh
       login                        |csh, ksh, sh
       logout                       |csh, ksh, sh
       nice                         |csh
       newgrp                       |ksh, sh
       nohup                        |csh
       notify                       |csh
       onintr                       |csh
       popd                         |csh
       print                        |ksh
       pushd                        |csh
       pwd                          |ksh, sh
       read                         |ksh, sh
       readonly                     |ksh, sh
       rehash                       |csh
       repeat                       |csh
       return                       |ksh, sh
       select                       |ksh
       set                          |csh, ksh, sh
       setenv                       |csh
       shift                        |csh, ksh, sh

       source                       |csh
       stop                         |csh, ksh, sh
       suspend                      |csh, ksh, sh
       switch                       |csh
       test                         |ksh, sh
       time                         |csh
       times                        |ksh, sh
       trap                         |ksh, sh
       true                         |ksh
       type                         |ksh, sh
       typeset                      |ksh
       ulimit                       |ksh, sh
       umask                        |csh, ksh, sh
       unalias                      |csh, ksh
       unhash                       |csh
       unlimit                      |csh
       unset                        |csh, ksh, sh
       unsetenv                     |csh
       until                        |ksh, sh
       wait                         |csh, ksh, sh
       whence                       |ksh
       while                        |csh, ksh, sh

   Bourne Shell, sh,  Special Commands
       Input/output redirection is now permitted for these commands. File descriptor 1 is  the  default  output  location.  When  Job  Control  is
       enabled, additional Special Commands are added to the shell's environment.

       In addition to these built-in reserved command words, sh also uses:

       :               No effect; the command does nothing. A zero exit code is returned.

       .filename       Read  and  execute  commands from filename and return. The search path specified by PATH is used to find the directory con-
                       taining filename.

   C shell, csh
       Built-in commands are executed within the C shell. If a built-in command occurs as any component of a pipeline except the last, it is  exe-
       cuted in a subshell. In addition to these built-in reserved command words, csh also uses:

       :               Null command. This command is interpreted, but performs no action.

   Korn Shell, ksh,  Special Commands
       Input/Output  redirection  is  permitted.  Unless otherwise indicated, the output is written on file descriptor 1 and the exit status, when
       there is no syntax error, is zero.

       Commands that are preceded by one or two * (asterisks) are treated specially in the following ways:

       1.  Variable assignment lists preceding the command remain in effect when the command completes.

       2.  I/O redirections are processed after variable assignments.

       3.  Errors cause a script that contains them to abort.

       4.  Words, following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a  vari-
           able  assignment.  This means that tilde substitution is performed after the = sign and word splitting and file name generation are not
           performed.

       In addition to these built-in reserved command words, ksh also uses:

       * : [ arg ... ] The command only expands parameters.

       * .file [ arg ..Read the complete file then execute the commands. The commands are executed in the current shell environment.   The  search
                       path specified by PATH is used to find the directory containing file. If any arguments arg are given, they become the posi-
                       tional parameters. Otherwise, the positional parameters are unchanged. The exit status is the exit status of the last  com-
                       mand executed. the loop termination test.

       intro(1), alias(1), break(1), cd(1), chmod(1), csh(1), echo(1), exec(1), exit(1), find(1), getoptcvt(1), getopts(1), glob(1), hash(1), his-
       tory(1), jobs(1), kill(1), ksh(1), let(1), limit(1), login(1), logout(1), newgrp(1), nice(1), nohup(1), print(1),  pwd(1),  read(1),  read-
       only(1),  set(1),  sh(1),  shift(1),  suspend(1),  test(1B), time(1), times(1), trap(1), typeset(1), umask(1), wait(1), chdir(2), chmod(2),
       creat(2), umask(2), getopt(3C), profile(4), environ(5)

                                                                    29 Jun 2005                                                  shell_builtins(1)
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