Manual Pages  — DPV

The dpv() config argument properties for configuring global display features:

struct dpv_config {
    uint8_t          keep_tite;     /* Cleaner exit for scripts */
    enum dpv_display display_type;  /* Def. DPV_DISPLAY_LIBDIALOG */
    enum dpv_output  output_type;   /* Default DPV_OUTPUT_NONE */
    int              debug;         /* Enable debug on stderr */
    int              display_limit; /* Files/page. Default -1 */
    int              label_size;    /* Label size. Default 28 */
    int              pbar_size;     /* Mini-progress size */
    int              dialog_updates_per_second; /* Default 16 */
    int              status_updates_per_second; /* Default 2 */
    uint16_t         options;       /* Default 0 (none) */
    char             *title;        /* Widget title */
    char             *backtitle;    /* Widget backtitle */
    char             *aprompt;      /* Append. Default NULL */
    char             *pprompt;      /* Prefix. Default NULL */
    char             *msg_done;     /* Default `Done' */
    char             *msg_fail;     /* Default `Fail' */
    char             *msg_pending;  /* Default `Pending' */
    char             *output;       /* Output format string */
    const char       *status_solo;  /* dialog(3) solo-status format.
                                     * Default DPV_STATUS_SOLO */
    const char       *status_many;  /* dialog(3) many-status format.
                                     * Default DPV_STATUS_MANY */

    /*
     * Function pointer; action to perform data transfer
     */
    int (*action)(struct dpv_file_node *file, int out);
};

enum dpv_display {
    DPV_DISPLAY_LIBDIALOG = 0, /* Use dialog(3) (default) */
    DPV_DISPLAY_STDOUT,        /* Use stdout */
    DPV_DISPLAY_DIALOG,        /* Use spawned dialog(1) */
    DPV_DISPLAY_XDIALOG,       /* Use spawned Xdialog(1) */
};

enum dpv_output {
    DPV_OUTPUT_NONE = 0, /* No output (default) */
    DPV_OUTPUT_FILE,     /* Read `output' member as file path */
    DPV_OUTPUT_SHELL,    /* Read `output' member as shell cmd */
};

The options member of the dpv() config argument is a mask of bit fields indicating various processing options. Possible flags are:

DPV_TEST_MODE	Enable test mode. In test mode, the action() callback of the config argument is not called but instead simulated-data is used to drive progress. Appends "[TEST MODE]" to the status line ( to override, set the status_format member of the dpv() config argument; for example, to DPV_STATUS_DEFAULT ).
DPV_WIDE_MODE	Enable wide mode. In wide mode, the length of the aprompt and pprompt members of the dpv() config argument will bump the width of the gauge widget. Prompts wider than the maximum width will wrap ( unless using Xdialog(1); see BUGS section below ).
DPV_NO_LABELS	Disables the display of labels associated with each transfer ( label_size member of dpv() config argument is ignored ).
DPV_USE_COLOR	Force the use of color even if the display_type does not support color ( USE_COLOR environment variable is ignored ).
DPV_NO_OVERRUN
	When enabled, callbacks for the current dpv_file_node are terminated when action() returns 100 or greater ( alleviates the need to change the status of the current dpv_file_node but may also cause file truncation if the stream exceeds expected length ).

The file_list argument to dpv() is a pointer to a "linked-list", described in <dpv.h>:

struct dpv_file_node {
    enum dpv_status    status; /* status of read operation */
    char               *msg;   /* display instead of "Done/Fail" */
    char               *name;  /* name of file to read */
    char               *path;  /* path to file */
    long long          length; /* expected size */
    long long          read;   /* number units read (e.g., bytes) */
    struct dpv_file_node *next;/* pointer to next (end with NULL) */
};

For each of the items in the file_list "linked-list" argument, the action() callback member of the dpv() config argument is called. The action() function performs a "nominal" action on the file and return. The return value of int represents the current progress percentage (0-100) for the current file.

The action() callback provides two variables for each call. file provides a reference to the current dpv_file_node being processed. out provides a file descriptor where the data goes.

If the output member of the dpv() config argument was set to DPV_OUTPUT_NONE (default; when invokingdpv()), the out file descriptor of action() will be zero and can be ignored. If output was set to DPV_OUTPUT_FILE, out will be an open file descriptor to a file. If output was set to DPV_OUTPUT_SHELL, out will be an open file descriptor to a pipe for a spawned shell program. When out is greater than zero, write data that has been read back to out.

To abort dpv(), either from the action() callback or asynchronously from a signal handler, two globals are provided via <dpv.h>:

extern int dpv_interrupt; /* Set to TRUE in interrupt handler */
extern int dpv_abort;     /* Set to true in callback to abort */

These globals are not automatically reset and must be manually maintained. Do not forget to reset these globals before subsequent invocations of dpv() when making multiple calls from the same program.

In addition, the status member of the action() file argument can be used to control callbacks for the current file. The status member can be set to any of the below from <dpv.h>:

enum dpv_status {
        DPV_STATUS_RUNNING = 0, /* Running (default) */
        DPV_STATUS_DONE,        /* Completed */
        DPV_STATUS_FAILED,      /* Oops, something went wrong */
};

The default status is zero, DPV_STATUS_RUNNING, which keeps the callbacks coming for the current file(). Setting ‘file->status’ to anything other than DPV_STATUS_RUNNING will cause dpv() to loop to the next file, effecting the next callback, if any.

The action() callback is responsible for calculating percentages and (recommended) maintaining a dpv global counter so dpv() can display throughput statistics. Percentages are reported through the int return value of the action() callback. Throughput statistics are calculated from the below global int in <dpv.h>:

extern int dpv_overall_read;

Set this to the number of bytes that have been read for all files. Throughput information is displayed in the status line (only available when usingdialog(3)) at the bottom of the screen. See DPV_DISPLAY_LIBDIALOG above.

Note that dpv_overall_read does not have to represent bytes. For example, the status_format can be changed to display something other than "bytes" and increment dpv_overall_read accordingly (for example, counting lines).

When dpv() is processing the current file, the length and read members of the action() file argument are used for calculating the display of mini progress bars ( if enabled; see pbar_size above ). If the length member of the current file is less than zero (indicating an unknown file length), a humanize_number(3) version of the read member is used instead of a traditional progress bar. Otherwise a progress bar is calculated as percentage read to file length. action() callback must maintain these member values for mini-progress bars.

The dpv_free() function performs free(3) on private global variables initialized by dpv().

dialog(1) does not display the first character after a series of escaped escape-sequences (for example, ``nbsp;' produces ``\'' instead of `` '). This is a known issue with dialog(1) and does not affect dialog(3) or Xdialog(1).

If an application ignores USE_COLOR when set and NULL before calling dpv() with color escape sequences anyway, dialog(3) and dialog(1) may not render properly. Workaround is to detect when USE_COLOR is set and NULL and either not use color escape sequences at that time or use unsetenv(3) to unset USE_COLOR, forcing interpretation of color sequences. This does not effect Xdialog(1), which renders the color escape sequences as plain text. See " embedded "\Z" sequences " in dialog(1) for additional information.