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Full Discussion: testing if files exist
Top Forums UNIX for Dummies Questions & Answers testing if files exist Post 302184875 by era on Sunday 13th of April 2008 01:17:26 PM
Old 04-13-2008
Is your script supposed to be invoked with the files you want to process, and terminate if they don't exist? $# indicates how many arguments there were (presumably you want to abort if there were none) but to check whether the named file(s) exist, you give them as arguments to "test -f".

Code:
case $# in 0) echo no files, try again >&2 ;; esac
for f in "$@"; do
  if [ -f "$f" ] ; then
    ... handle file
  else
    echo "$0: file $f not found -- skipping" >&2
  fi
done

 

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POPEN(3)								 1								  POPEN(3)

popen - Opens process file pointer

SYNOPSIS
resource popen (string $command, string $mode) DESCRIPTION
Opens a pipe to a process executed by forking the command given by $command. PARAMETERS
o $command - The command o $mode - The mode RETURN VALUES
Returns a file pointer identical to that returned by fopen(3), except that it is unidirectional (may only be used for reading or writing) and must be closed with pclose(3). This pointer may be used with fgets(3), fgetss(3), and fwrite(3). When the mode is 'r', the returned file pointer equals to the STDOUT of the command, when the mode is 'w', the returned file pointer equals to the STDIN of the command. If an error occurs, returns FALSE. EXAMPLES
Example #1 popen(3) example <?php $handle = popen("/bin/ls", "r"); ?> If the command to be executed could not be found, a valid resource is returned. This may seem odd, but makes sense; it allows you to access any error message returned by the shell: Example #2 popen(3) example <?php error_reporting(E_ALL); /* Add redirection so we can get stderr. */ $handle = popen('/path/to/executable 2>&1', 'r'); echo "'$handle'; " . gettype($handle) . " "; $read = fread($handle, 2096); echo $read; pclose($handle); ?> NOTES
Note If you're looking for bi-directional support (two-way), use proc_open(3). Note When safe mode is enabled, you can only execute files within the safe_mode_exec_dir. For practical reasons, it is currently not allowed to have .. components in the path to the executable. Warning With safe mode enabled, the command string is escaped with escapeshellcmd(3). Thus, echo y | echo x becomes echo y | echo x. SEE ALSO
pclose(3), fopen(3), proc_open(3). PHP Documentation Group POPEN(3)
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