file_utils.h File Reference

#include <stdbool.h>
#include <stddef.h>

Go to the source code of this file.

Functions
bool	write_file (const char *const path, const char *const value)
bool	read_first_line_from_file (const char *const path, char *line, size_t len)

Detailed Description

Helper functions to read and write files.

Definition in file file_utils.h.

Function Documentation

read_first_line_from_file()

bool read_first_line_from_file	(	const char *const	path,
		char *	line,
		size_t	len
	)

Read the first line from a file into a buffer passed by caller.

Parameters

[in]	path	file path
[in,out]	line	function reads 1st line from path and puts it in this parameter
[in]	len	length of line

Returns

true on success, else false

Definition at line 212 of file file_utils.c.

                                                                               {
    FILE* f = fopen(path, "r");
    if(!f) {
        SAH_TRACEZ_ERROR(ME, "Failed to open %s: %s", path, strerror(errno));
        return false;
    }
    bool rv = true;
    if(!fgets(line, (int) len, f)) {
        SAH_TRACEZ_ERROR(ME, "Failed to read from %s", path);
        rv = false;
    }
    if(fclose(f) == EOF) {
        SAH_TRACEZ_ERROR(ME, "Failed to close %s: %s", path, strerror(errno));
    }
    return rv;
}

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write_file()

bool write_file	(	const char *const	path,
		const char *const	value
	)

Write the string value to the file path.

Parameters

[in]	path	file path
[in]	value	value to write to path

If path already exists and has value as contents, the function immediately returns true to avoid an unneeded write.

The function first writes the value to the file path with ".tmp" appended. Then it renames the file to path.

Returns

true on success, else false

Avoid writing the file if the file already exists and already has the value of the parameter 'value' as contents.

Definition at line 154 of file file_utils.c.

                                                                 {
 
    SAH_TRACEZ_DEBUG2(ME, "path='%s' value='%s'", path, value);
 
    const size_t value_len = strlen(value);
    if(value_len >= LINE_LEN) {
        SAH_TRACEZ_ERROR(ME, "strlen(value) = %zd >= %d", value_len, LINE_LEN);
        return false;
    }
    if(access(path, F_OK) == 0) {
        SAH_TRACEZ_DEBUG2(ME, "%s already exists", path);
        bool has_value = false;
        if((check_file_has_value(path, value, &has_value) == true) && has_value) {
            return true;
        }
    }
 
    char tmpfile[256];
    if(snprintf(tmpfile, 256, "%s.tmp", path) < 0) {
        SAH_TRACEZ_ERROR(ME, "%s: failed to create path with .tmp", path);
        return false;
    }
 
    FILE* f = fopen(tmpfile, "w");
    if(!f) {
        SAH_TRACEZ_ERROR(ME, "Failed to open %s: %s", tmpfile, strerror(errno));
        return false;
    }
 
    bool rv = true;
    if(fputs(value, f) == EOF) {
        SAH_TRACEZ_ERROR(ME, "Failed to write to %s", tmpfile);
        rv = false;
    }
 
    if(fclose(f) == EOF) {
        SAH_TRACEZ_ERROR(ME, "Failed to close %s: %s", tmpfile, strerror(errno));
    }
    if(!rv) {
        return false;
    }
    return rename_file(tmpfile, path);
}

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